When faced with any design decision, the first step is to gather all necessary information. After that's done, it's best to go with your gut and be confident in the decision you feel best about.  Everyone understands that things change and when you find a decision you made wasn't the best...own up to it immediately and go with a new plan.

Approaching design decisions this way helps the team to move forward quickly and also helps build their confidence in you.  They will begin to know you as a person of action and will trust you for quick feedback that won't keep them waiting.  If you find that you are having to consistently own up to bad decisions...well at that point you should start evaluating your decision process :)