Quote from dmo:
The point is not to buy strangles, or call/put spreads, or calendar spreads. The point is to find an edge. You have to have a reason to believe there's a better-than-random probability of something in particular happening. Once you determine that, you look for a way to play that with options without paying more-than-random-probability prices.
All the "strategies" such as vertical spreads, strangles, etc. are just possible ways to formulate an actual play from your opinion. None of them should be seen as having particular value in and of themselves.
A lot of people here seem to have this idea that if it's Monday, it's time to do xyz strategy. Personally, I think the most important attribute in a good trader is the patience to wait until a juicy play presents itself, and the discipline to do nothing until then.