Decisive explains the WRAP process, a methodology for decision-making. If you've read about cognitive biases before, you'll feel right at home. While reading it, I've succesfully used the WRAP for one decision of my own and as advice for an NGO planning an event. On both counts it was the key to getting unstuck.

Here's the process in short (excerpt from the free one-pager available here):

W - Widen your options
Narrow framing leads us to overlook options. (Teenagers and executives often make “whether or not” decisions.) To solve this, we can
1. uncover new options e.g., by finding someone who has solved your problem
2. consider options simultaneously through multitracking. (Think AND, not OR.)

R - Reality-test your assumptions
In assessing our options, the confirmation bias leads us to collect skewed, self-serving information. To combat that bias, we can
1. ask disconfirming questions (What problems does the iPod have?)
2. zoom out (How many people with similar expertise as mine have passed this exam?)
3. zoom in (Personally trying out a competitor's product, not relying on just hard numbers)

A - Attain distance before deciding
Short-term emotion tempts us to make choices that are bad in the long term. To avoid that, we need to attain distance by shifting perspective.
1. What would I tell my best friend to do?
2. What would my successor in this professional role do?
3. What are the consequences of the decision in 10 minutes, 10 months and 10 years?

P - Prepare to be wrong
We are overconfident, thinking we know how the future will unfold when we really don’t.
1. Prepare for bad outcomes (pre-mortem)
2. Prepare for good outcomes (pre-parade).