Build your intelligence over time. If it takes you several months to slowly piece things together you end up with valuable information. Information goes stale quickly in today's business environment. Strategy is very important. Strategy is usually the most important thing you can learn about a competitor.
Details are sometimes hard to find but the overall strategy is often easy to determine.
If your voice and face are known consider using someone else to do the investigating. Remember no one knows your mission but you. Keep the results you want in focus. Be sure to get all printed materials that are given out. This material can give a lot of detail, help determine the organizational chart, show general strategy, name key people, etc.