1) Avoid or limit being around people who make you susceptible to smoking. People and environment have an influence on you and your choices. Be careful of who you surround yourself with and the places you go.
2) If you have someone that you buy from, either delete, or block and delete their number. By doing this, you will no longer be tempted to buy and smoke.
3) Get rid of all your existing stuff. A friend of mine flushed his weed down the toilet because he wanted to stop. If you do not have access to it, you will be less likely to smoke.