Tayammum if you didn't find water or cannot perform Wudu or Ghusl

And if you are ill or on a journey or one of you comes from the place of relieving himself or you have contacted women [i.e., had sexual intercourse] and find no water, then seek clean earth and wipe over your faces and your hands [with it]. Indeed, Allah is ever Pardoning and Forgiving Suratu An-nissaa verse 43 - Chapter 4 Verse 43

In Sunnah we find the Hadith of the prophet Mohamed (prayers of ALLAH upon him) said: "The earth has been made for me (and for my followers) a place for praying and a thing to perform Tayammum..." From Sahih AL-Bukhari 438

Tayammu or dry Ablution : In Arabic, the word Tayammum literally means an 'aim' or 'purpose.' In Islamic Law, it refers to: 'Aiming for or seeking soil to wipe one's face and hands with the intention of purification and preparing oneself to pray, and so on ! And it is a blessing from ALLAH subhanahu wa Tâala

When can we make Tayammum ? well , we cannot perform Tayammum as we wish ! But there are specific cases 

 If one cannot find water or the amount one finds is insufficient for ablution

If one thinks that using water will worsen it (he does not have to be absolutely sure, but may base his assumption on past experience or what a knowledgeable person has told him), he 

may perform Tayammum

Tayammum is allowed when water is available but is too cold and cannot be heated, or there is no public bathroom available

If one fears for his life, family, wealth, [for example, if an enemy (beast or human) is nearby or if one is a prisoner, and so on], he may perform Tayammum. This is also allowed if there is water but one lacks the proper means to get it, or if one fears some accusation against him if he gets it

If one is saving his water for later use because of drought or if he is in a long trip with no enough water

 If one can get water, but fears that the prayer will be over by the time he gets it He can perform Tayammum and pray, and does not need to repeat his prayer after he gets water

The Soil Used for Tayammum must be pure, clean, natural soil: this can be sand, stone, gypsum, and so on but not artificial like building cement or plaster ...etc

How to Perform Tayammum

How to Perform Tayammum? It is easy way ! Firstly he must have the intention to perform ablution and purifying himself, then he mentions Allah's name (Bismillah), strikes the soil with his hands, and wipes his face and hands up to the wrist, starting with the right hand

What Tayammum Makes Permissible

After performing Tayammum, one is pure and may perform any of the acts requiring prior ritual purification, such as praying and touching the Quran. He does not have to perform it during the time of prayer, and he may pray as many prayers as he wishes (unless he nullifies it), exactly as it is the case with regular ablution

This is a helpful video to learn how perform Tayammum May ALLAH Subhanahu Wa Tâala accept yours

https://www.youtube.com/watch?v=d29NUhj1ZsM