Watch your initial assumptions. We have a tendency to look for information that supports rather than contradicts our current view.
Value your information source - as well as the information. People tend to put more weight on friends' views than they do on research from a reliable source.
Choose criteria for assessing the options if a group of you can't agree on a decision. Judge each alternative against them. Alternatively, make sure you all agree on the question you're trying to answer.
Don't rely on shaky logic. It's easy to be persuaded to take a course of action because of the effort that has already gone into making it happen. Instead, base your decision on your best assessment of its implications.
Roll a dice. If you are stuck between several options, allocate a different number to each option. If you aren't happy with the number that comes up, dismiss this option, and roll again. This will force your real preferences to the surface.
Give equal consideration to all discoveries. When taking in information to make our decisions, we pay more attention to what we discover first and last. Make an effort to give fair weight to what you learnt in between.
Imagine the decision has been made. Think about what is likely to happen as a result. By immersing yourself in the future, you can discover implications that weren't previously obvious.
Talk it through. Before you make a significant decision, discuss it with someone who is unlikely to agree. Their challenge will help you ensure your thinking is rigorous.
Leave time to think it over. It can help to leave time before making a decision to allow your unconscious mind to mull on it. But set yourself a deadline, otherwise procrastination may set in.