Know what type of information is needed before you attempt to go after information. Bringing in lots of unnecessary information and data is a waste of time. Once you determine the type of information that is needed you can set up a plan. If you have a number of competitors put the information on a spreadsheet. Use the World Wide Web and Internet to research first.
Much information is freely available and easily accessible.
Look at their website. I always run a search on Alta Vista before doing anything else. If you are on speaking terms with your competitors consider just asking them. If you are perceived as a nice person and non-threatening you can get results this way. Be aware that many managers and owners will distort information to make things seem better or worse.