This prayer (chalisa) praises the Lord and asks for his help in removing all the problems from the devotees life. It is suggested that you focus your mind on Lord Shiva or his image and say this prayer.

Jai Ganesh Girija suvan, mangal mool sujan,
Kahati Ayodhyadas tum, deu abhaya vardan.

Hail Lord Ganesh, son of Girija, who is supremely wise and the start of all auspicious events. Ayodhyadas asks you, to grant him the boon of safety and security.

Jai Girijapati deen dayala,
Sada karat santan pratipala.

Hail Girijapati (Shiv, husband of Girija. Girija means mountain, referring to Mt. Kailash, where Lord Shiv is supposed to reside.), the ever kind lord,
Who always looks after and protects his devotees.

Bhal chandrama sohati neeke,
Kanan kundal nag phani ke.

He has the moon upon his forehead,
and in his ears, instead of rings, he has the serpents coiling around.

Ang gaur shiv ganga banai,
Mundamal tan kshar lagai.

He is fair complexioned with the divine river, Ganga, flowing from his crown,
Around his neck, he has a necklace of severed heads and his body is smeared with ash.

Vastra khal baghambar sohe,
Chhavi ko dekh nag muni mohe.

He wears the skin of a panther tied around his waist,
Looking at his charming view, the serpents and high sages get enchanted.

Maina Matu ki priya dulari,
Bam ang rajat Shiv pyari.

The beloved daughter (referring to Parvati) of Maina is sitting on his lap at his left side,
She is supremely dear to Lord Shiv.

Kar men soha trishul ati bhari,
Karahi sada shatrun samhari.

He carries a heavy trident in his hand,
with which he slays the enemies forever.

Nandi Ganesh soh tanha kaise,
Manas madhya kamal hon jaise.

With him are Nandi (the bull) and Lord Ganesh,
Looking as beautiful as lotus flowers blooming in Mansarovar lake.

Kartik shyam aur gana rauo,
Ya chhavi barnat bane na kauo.

He has with him dark complexioned Kartikeya and Ganesh (his sons),
No one is capable to describe the full spectacle.

Devan jab hee aai pukara,
Tabahin dukh prabhu ap nivara.

Whenever the celestials (devas) faced problems and came to you,
You always solved the problems and provided succour to them.

Keen upadrava tarak bhari,
devan sab mili tumhari pukari.

When the demon Tarak wrought havoc,
The celestials all called to you help.

Turat shadanan ap pathayo,
Luv nimesh mahi mar girayo.

Then you immediately sent Sadanand (the six faced Kartikeya),
Who, within no time at all, destroyed the demon.

Ap Jallandhar asur sanhara,
Suyash tumhar vidit sansara.

You also slayed the demon, Jallandhar,
Your glory is well known to the world.

Tripurasur sang yuddha machayi,
sabahin kripa kari leen bachayi.

By fighting and killing the Demon Tripurasur,
You forgave everybody and saved the Gods.

Keenha tap Bhagirath bhari,
Purahi pratigya tasu purari.

King Bhagirath 1 had performed a rigorous penance,
And by you grace, you fulfilled his wishes.

Darpa chhod Ganga tab ayee,
Sewak astuti karat sadaee.

Because of this, Ganga (the river), left her abode and came to earth,
That is why your devotees always sing your praise.

Ved naam mahima tav gayaee,
akath anadi bhed nahin payee.

The Vedas had tried to describe your glory but the same is beyond explanation,
It is impossible to fathom your full glory.

Pragati udadhi manthan te jwala,
Jare surasur bhaye bihala.

The sea churning 2 had produced such a dreadful poisonous flame,
Which scared both the Gods and demons.

Mahadeva tab kari sahayee,
Neelkantha tuv nam dharayee.

The, Great God, you came to their rescue and drank the poison,
Which stayed in your throat, making it blue, hence you are called Neelkanth (Blue throated one)

Poojan Ramchandra jab keenha,
Lanka jeet Vibhishan deenha.

When Lord Ram 3 worshipped you,
You gave him victory over Lanka and made Vibhishan it's king.

Sahas kamal arpanahi vichari,
Keenha pareeksha tabahi purari.

During this worship, Lord Ram decided to offer you a thousand lotus flowers,
Then to assess his firmness of faith, you decided to test him.

Ek kamal Prabhu rakheu goyee,
Kamal nayan poojan chahin soyee.

Lord, you decided to hide one of the flowers,
Not finding it, Lord Ram substituted his lotus like eye for it.

Kathin bhakti dekhi Prabhu Shankar,
Bhaye prasanna deya icchhit var.

Lord Shanker was pleased with his (Ram's) steadfast devotion,
You granted him the desired boon (of slaying Ravaana).

Jai Jai Jai, Ananta Avinasi,
Karat kripa sab ke ghatvasi.

Hail to thee, O Infinite and Indestructible Lord,
Shower your grace on everybody, O Omniscient one.

Dushta sakal mohi nitya satavan,
Bharmita rahe man chain na aven.

I am always troubled by wicked people,
This makes me distressed with no peace of mind.

Trahi trahi main nath pukaro,
Yeh avasar mohi, ani ubaro.

Getting distressed, I pray to you, Lord Shanker,
O Lord, help me in these troubled times.

Lai trishool shatrun ko marau,
Sankat se mohi ani unarau.

Come with your trident and slay my enemies,
And free me from my problems.

Mata pita bhrat sab hoi,
Sankat mein poonchat nahi koi.

Although I have my mother, father, brothers and family,
Yet in times of trouble, nobody offers me help.

Swami ekahi aas tumhari,
Ai harahu sab sankat bhari.

O Lord, you are my only hope,
O Master, please come and take away this heavy burden (problems).

Dhan nirdhan kon det sadaee,
Arat jan ki peer mitaee.

You give wealth to the poor,
And you wipe away their difficulties.

Astuti kehi vidhi karahu tumhari,
Shambunath ab tek hamari.

I do not know of any other way to seek your help from my problems,
Hey, Shambunath, listen to my prayer now.

Shanker ho sankat ke nashan,
Vighna vinasan mangal karan.

Shankar, you are the destroyer of problems,
Please be the root of my happiness and welfare

Yogi yathi muni dhyan lagaye,
Sharad Narad Sheesh navavahin.

All the sages and yogis meditate on you,
Saraswati (Goddes of Wisdom), Narad (son of Brahma) and the seers bow in reverence to you.

Namo namo jab namah Shivaye,
Sur brahmadik par na paye.

I now chant your name, "Om Namah Shivaye",
Neither Brahma not the Gods could fathom your entire glory.

Jo yeh path kare man layee,
To kon hot hain shamboo sahayee.

Whoever reads this prayer with utmost devotion,
Shall definitely be helped by Lord Shamboo, without any doubt.

Putra na ho, ichha kare koi,
Nishchaya Shiv prasad se hoi.

Anybody without a son who prays to you,
Will definitely be blessed with one by Lord Shiv.

Pandit triyodashi ko lave,
Dhyan poorvak hom karave.

The devotees should get a priest to perform a yagna (prayer) on the 13th lunar day of the fortnight,
And with full attention and devotion, one must pray to Lord Shiv to get their wishes fulfilled.

Triyodashi vrita kare hamesha,
Tan nahi take rahe kalesha.

Whoever fasts on the thirteenth day of the lunar fortnight,
Gets peace of mind and a healthy body.

Dhoop deep naivedya chadhavahi,
Shanker sanmukha path karavahi.

With a lighted lamp, incense and other payer material,
One should worship before an idol of Lord Shiva with full devotion.

Janam Janam ki pap nasavahin,
Antawas shivpur men pavahin.

A devotee of Shiv will have all the sins (karmas) of all his births wiped away,
And in the end, he will live happily in the kingdom of Lord Shiva.

Hey Shankar hai aas tumhari,
Dukh peera ab harahu hamari.

O Lord Shanker, you are my only hope,
Now please end all my pains and worries.

This refers to the time when the earth was faced with a severe drought. The then ruling king, Bhagirath performed a powerful penance for water to come to earth. The only hope was for the river Ganga to come down to earth from heaven. But the force of her was such that the realm would be destroyed. The only God who could control her descent was Lord Shiva, who trapped her in his hair. Hence in all images of Lord Shiva, we see the river Ganga flowing from his hair.
At the time of creation, certain powers were required by the Gods. The only way to get those powers was to churn the ocean of creation. As this churning was too great for even the Gods to perform, they enlisted the help of the demons. Before they could get the powers, the churning would release a poison that would destroy all the Gods, demons and the universe. Lord Shiv agreed to swallow this poison as only he had the power to do so. When the poison appeared, he swallowed the same. But his spouse, Goddess Parvati, fearing that her husband would die of the poison, held his throat, preventing the poison from going down any further. Hence, the poison stayed in his throat, making it the colour of dark blue
Ravaana was a great devotee of Lord Shiva, and Shiva had blessed him that he could not be destroyed. Lord Ram knew of this, and he knew that the only solution was to pray to Lord Shiv to rescind that boon given to Ravaana so that Lord Ram could kill Ravaana. (This is from the Ramayana)