B.,
My son is 28 months old now and we stopped at 26 1/2 months. He was not ready, but I was ready. So, at 22 months, I began the weaning process. I started it early because I did not want it to be a traumatic experience for him. Every week, I would take away one nursing session. As we progressed along the way, each week would include one, two, and then, close to the end, three. In the final two weeks, he was having a really hard time. But,, I stuck to my guns, and held him more during the day, did not sit down at all, and kept him busy with activities all day long. Night nursing was the last to go, as we cosleep together. The final day, I decided to tell my son a story, he is very smart, so it worked great. I told him that there is this little boy screaming with hunger because his mommy does not have milk. The stork (showed him a photo) came and took his milk from my boobies and carried it to the mommy so she could feed her starving boy. He began to scream, No, No. Then, I proceeded to tell him that he has teeth and is able to eat wonderful things like meatballs, ice cream, carrots, brocolli, and all the fun and exciting things that little babies can not eat because they do not have teeth and need milk. But, he is a little boy now and has lots of teeth. Anyway, the more I explained that the little baby was crying and needed the milk because he did not have teeth, the more he was okay with giving his milk away. I still tell him this story every now and then when he wants to hold a boob and ask for milk.
My suggestion to you is make certain this is the time for you and your son to let go of the nursing. Because once it is gone, that's it! DO NOT let others, immediate family members especially, pressure you into quitting. Both my Mom & Mother-in-law would have had me quit by 12 months. As you can see, I do not let other people make such an important decision for me and my son. If you are ready, start the process. If you are doing this because of pressure from spouse, etc....Become knowledgeable on the nursing and share your knowledge with these individuals. I used these weapons everytime someone started in on me about nursing so long.
Wish you and your son the best! Good luck!