Its easy to be able to hypnotize yourself once you know how. Furthermore, it gets easier and easier to hypnotize yourself after a small amount of practice. I would suggest however before you do anything is to get hypnotized with a trained professional. This is in order to understand what the process is actually like and to help familarize yourself with this process. You may also like to ask the hypnotherapist to teach you the basics during this first session.

Regardless, the first thing you should do to hypnotize yourself is to sit or lie down in a comfortable spot. It shouldn't be too comfortable that makes you fall asleep so i suggest at least the first few times you sit in a comfortable chair with your head up. Start by breathing deeply, and breathing out. Do this several time with the attention on your breathe. Following this you should look at an object or spot in the room you are in. Focus your attention on this spot and say to yourself out loud three obvious things that can be said visually about this spot. For example, if you're looking at a doorhandle. You say out loud

"The door handle has the color white"
"The door handle has a shiny surface"
"The door handle is large"

After making 3 visual comments, make 3 audio comments that you can hear in the room you are in. These maybe sounds that you hear outside the room - ie birds chirping, people talking or cars going past.

"I hear people talking in the other room"
"I hear cars driving past the window"
"I hear birds chirping outside"

Then make 3 statements concerning things you can feel

"I feel the surface of the chair on my back"
"I feel my feet fit comfortably in my shoes"
"I feel the air on my skin"

Then say out loud or in the mind

"I am going deeper and deeper into a hypnotic state and my mind relaxes even further"
"For the next x minutes i will seat/lie in a calm, peaceful, hypnotic state in full awareness"

The next comments should be those that you wish to make. These suggestions are much more likely to be taken on by the concious mind because they're being spoken in the hypnotic state. If you're trying to quit smoking, you can add quit smoking hypnosis suggestions which will help you quit smoking by hypnosis.