Any advice on how to make quick decisions at a large organization without wasting time discussing possibilities and not getting anything done?

A tool I use often is weighted decision matrix and rational decision making process. 

Step 1: Collect ALL the deliverables, decision criteria (formal and informal
Step 2: Select "must have" from "normal"
Step 3: With management weight all criteria for importance (1 to 10)
Step 4: Identify decision options (source from stakeholders, market, etc.)
Step 5: If an option does not meet the "must have" criteria, exclude it but keep it in the roster for visibility
Step 6: score according the criteria (1 to 10)
Step 7: Calculate Weighted score (Sum of (Decision Criteria Score * Weight))

Keep details of the scoring rationale.

Present to executives for validation. 

Here's a strategy that's worked for me: First, set a clear agenda before any meeting and stick to it. Allocate specific time for discussions and decision-making. Second, empower smaller, cross-functional teams to make decisions; they're often closer to the details and can move faster. Third, adopt a "disagree and commit" philosophy. It's okay for everyone to voice their opinions, but once a decision is made, everyone commits to it. Lastly, always be data-driven. Having clear data points can cut through a lot of subjective debates.

It starts with setting the right expectations, having clear deadlines, and understanding what the dependencies to that decision is. For example: Do we need experts? Which part of the organization do we need? With products today, there are so many parts that need to come together that depend on what the decision is about. Figuring out who needs to be part of that decision, who needs to build it or participate in the conversation and understanding the organization at large is key. But you also want to limit the number of people involved as you don’t want management that don’t necessarily need to be there to be the bottleneck for decisions. Structure is important 

For day to day decisions, push back on people so that they can make those decisions themselves. Empower people and trust in their knowledge and decisions. 

Having well-thought out options with positives and negatives plus a recommendation can work.  Having something for people to react to can help narrow the conversation quickly vs. an open-ended conversation.  Another idea is to state at the beginning of the meeting that "The goal is to leave here with a decision about ..."

I always start with a recommendation.  Have the smallest group possible come up with the "answer" then pose alternatives as "things considered".  It stops from having the larger org / group spend time on 10 alternative paths.  Maybe you have to re-open 1 or 2 of them, but then it is just in comparison to the recommendation.