Depending on the SSD, you don't need anything extra except to make sure you have an extra SATA cable to connect to the MOBO. If you don't have a SATA cable pick up one to connect the SSD to your MOBO.
Some come with the required 2.5" to 3.5" adpator that is required. Just check your SSD box contents to see if it has an adpator and if it doesn't pick up one from where you are buying it from.
Make sure your PSU has a free SATA power connector too