The Internet can help you make it through the difficult times when you made your decision and have doubts and are tempted to fall back.

To optimally face the risks and avoid the pitfalls, you better be informed about what to expect and what you will encounter. The site of ASH (Action on Smoking and Health) describes what the beneficial health changes are when you stop smoking. Reading this might motivate you. They also describe the duration of the withdrawal symptoms. Please refer to their factsheet (11)

The ASH also has 15 tips (extraction of factsheet 24):

1. Get professional help. Your doctor, pharmacist, or health visitor should also give advice and they should tell you if there are special services for smokers in your area. See also ASH's quitting links for further help and resources.
2. Prepare mentally. You are not alone! 70% of British smokers would like to quit and about three million try each year. More than 11 million people in Britain have quit and are now ex-smokers. However, it can be tough and you will need lots of willpower to break the hold of nicotine - a powerful and addictive drug. An important part of this is to know what you would gain and what you would lose from stopping smoking.
3. Demolish smoking myths. Soon after smoking a cigarette the body and brain start to want more nicotine and many people begin to feel increasingly uncomfortable until they have the next cigarette. Smoking feels pleasurable, but much of the pleasure of smoking is relief of withdrawal from nicotine. There are times that many people feel distracted or unable to enjoy themselves because you they were not able to smoke. This is nicotine withdrawal in action. If you see it this way, cigarettes are not a familiar friend but more like a greedy parasite demanding constant attention.
4. Understand what to expect. Most people find the first few days difficult and for some it can be a long struggle, but things will typically start to get better after the third or fourth day. Nicotine withdrawal may make you restless, irritable, frustrated, sleepless, or accident prone - but these things will pass and you will quickly start to feel the benefits. See the ASH fact sheet on what happens when you give up smoking.
5. Make a list of reasons why you want to stop smoking. It means different things to different people, but if you know what you want from stopping, it could help you through the most difficult moments.
6. Consider the money. (smoking 20 a day can cost £1,600 per year).
7. Set a date. Some people make a New Year's Day resolution, others pick their birthday, and you can join in with others on No Smoking Day - the second Wednesday of every March - when up to a million smokers have a go. Any day will do, but choosing a date will help mental preparation.
8. Involve friends or family. If you live with someone else that smokes, it will be much easier to quit if you do it together.
9. Deal with nicotine withdrawal.Nicotine is a powerful addictive drug (see ASH fact sheet on nicotine) and you can roughly double the chances of successfully quitting smoking by using nicotine replacement therapies such as patches, lozenges, inhalers, and/or gum. The idea is to come off nicotine gradually by using a low nicotine dose to take the edge off the cravings and have a 'soft landing'.
10. Other treatments may help. Hypnosis, acupuncture or other treatments may help some people, but there isn't much formal evidence supporting their effectiveness.
11. Find a (temporary) substitute habit. Smoking also involves having something to do with the hands or mouth.
12. Deal with any weight-gain worries. Yes it is true: many people do gain weight when they quit smoking. Nicotine changes the appetite and body's energy use (metabolism).
13. Avoid temptation. In the difficult first few days you can change your routine to avoid situations where you would usually smoke. For example, it might be worth avoiding the pub on the first Friday night after you quit.
14. Stop completely. Although it might seem like a good idea to cut down and then stop, this is actually very difficult to do in practice. If you cut down, the likely response is that you will smoke each cigarette more intensively and end up doing yourself just as much harm. The best approach is to go for a complete break and use nicotine replacement products (see above) to help take the edge off the withdrawal symptoms.
15. Watch out for relapse. You will need to be on your guard especially in the first few days and weeks. "I'll have just one, it can't harm" is the top of a long and slippery slope. If you are upset or under pressure, it is really important to fight off the temptation to smoke - don't let this be an excuse for slipping back. You could lose everything you've achieved just in a momentary lapse.
    
    Also The Cancer Organization has made a guide for quitting smoking. We cite from their tips for Dealing With Withdrawal

One way to overcome these urges or cravings is to recognize rationalizations as they come up. A rationalization is a mistaken belief that seems to make sense at the time but is not based on facts. If you have tried to quit before, you will probably recognize many of these common rationalizations.

• I'll just use it to get through this rough spot.
• Today is not a good day; I'll quit tomorrow.
• It's my only vice.
• How bad is tobacco, really? Uncle Harry chewed all his life and he lived to be over 90.
• You've got to die of something.
• Life is no fun without smoking.
• You probably can add more to the list. As you go through the first few days without tobacco, write down any rationalizations as they come up and recognize them for what they are: messages that can trap you into going back to using tobacco. Use the ideas below to help you keep your commitment to quitting.