Moving your infant from cot to bed can be a real headache, with some infants showing real resitance to the move. As with most things kid related, it's important to look out for their readiness cues, and where possible not rush the process. Obviously, sometimes timing can be out of controls, when perhaps a cot is needed for a new baby.
There are many strategies you can employ for when the time comes, and one thing that really worked for our little guy was really involving him in the process. We got him to help choose his bed, and more importanly his bedding. Our little guy opted for a Fireman Sam bedding set, so when the time came for him to move to his new bed, he was super excited about getting to sleep in a whole bed of Fireman Sam. By allowing him to make certain choices, he felt really involved and this definitely made for an easier transition than we'd anticipated.