Depending on the source that you are using, RCTs and CCTS can be identified in a number of ways. For example, you could use the Cochrane Highly Sensitive Search Strategy for identifying randomized trials in MEDLINE.

There is also a Cochrane Highly Sensitive Search Strategy for identifying controlled trials in Embase available. 

For less sensiteive searching, there are also options within databse search interfaces and the following are available in OVID:

• RCTs are assigned the Publication Type 'Randomised Controlled Trial';
• CCTs are assigned the Publication Type 'Controlled Clinical Trial' (but check to ensure that the CCT label matches the Cochrane criteria for a CCT).

There is a Training manual for handsearchers, hosted by the Cochrane Information Retrieval Methods Group. This guide was produced in 2002, but the content is still current.