How to draw tree diagram

I have the following problem from my home problem.

An oil-prospecting firm hits oil or gas on 10% of its drillings. If the firm drills two wells, the four possible events and three associated probabilities are shown below.

Out come of 1st drilling
There are 4 events
1 Hit (oil or gas)
2 hit
3. miss
4 miss

Outcome of 2nd drilling
there are also 4 events
1 Hit (oil or gas)
2 Miss
3 Hit
4 miss

Construct a tree diagram to represent this experiment.

I just wonder if someone can help me how to approach to draw a tree diagram.