We are in the process of this right now (DD 14mo)
We decided to start the transition because she was nursing allllll night long and would wake if I tried to unlatch her, yet her latch was getting lazy and shallow overnight which was causing me a LOT of pain. The more she would nurse, the worse the pain got. Plus, her constant wakings was waking me up. We were both sleep deprived and grumpy. She starting to take over our bed to where I am having a some difficulty getting comfortable. If DH joins us, it is a long night for all, LOL. So we hope to eventually move her into her toddler bed across the room.
We started last weekend, just working on setting limits to the night nursing first. I nursed her to drowsy, unlatched her, and said "milk is all done". She was very angry about this the first two days. She'd roll away from me and sob, but she did eventually allow me to cuddle her and rub her back, and soon she'd sleep. For her night wakings, I offered her more back rubs and cuddles. She could nurse again when morning came.
By Day 3, she took it all as a matter of course. She disapproved of milk being "all done" but quickly settled into our new routine of cuddling. She woke twice that night.
Day 4, she slept all night long. For the first time ever! Last night she had a couple night wakings, in which I allowed the boob.
Naps have been a little more challenging. She goes down no problem without needing the nipple in her mouth, but will wake after an hour obviously still tired, and no amount of soothing will get her back to sleep.
For the most part, it is going well.
Once we are established in this new routine and she is reliably sleeping with <2 wakings, we will work on transitioning her to her toddler bed, at first for the beginning of the evening, and then for most or all of the night. It will be done a similar way as night weaning. I'll nurse her in bed (or in the rocker), milk will be "all gone", and then I'll lay her down in her bed with me sitting next to her on the floor, rubbing her back, shhhhing, etc.