Do not fear my friends, for being the beer geek that I am, I have gone ahead and done some field-work to get some crystal clear answers. The problem is, you might not like the result...
There are quite a few sites I found that give a good explanation on what beer glass suits what style and "how the glass works" to improve your experience, but instead of re-inventing the wheel and spinning someone else's articles here are some links:
http://www.craftbeerware.com/beer-glass-types
http://www.beerwrangler.com/the-beer-glass-guide/
1) type of beer to be consumed
2) my mood/setting...which technically affects the choice in number one anyway
Keeping 20 different glasses is not that practical, so I basically have three glasses in heavy rotation. My primary choice for just about any beer that I plan to sit down and enjoy will be a snifter. Whether I am trying a new beer, tasting one of my own concoctions or if I eventually have the heart to open up one of my speciality beers from the collection, the snifter does a pretty excellent job. Actually to be honest this is the glass I sip my Blockhouse from after a long day at the office or to accompany my Saturday night stout and spagbol. The glass shape helps to taper the aroma of the beer as you take a sip to concentrate all the lovely smell into the taste and has kind of become my go-to glass.
Then of course there are the days when you need to have an Amber Weiss or sit back with a Bonecrusher from nothing other than one of the Weiss style glasses. Open topped to produce that wonderful aroma and keep that head thick whilst tall and curvy to show off that murky carbonation and give the perfect grip size in the middle.
Imagine ordering a Vannie Hout from The Taproom, and they brought you three weiss glasses instead of the suave, Devils Peak branded snifters? Imagine all those guys ordering a Castle LITE and getting it in a snifter...no more "it's already in a glass, boet!". So maybe in a taproom/pub setting the glass (or lack thereof) might also hint at what to expect from that pint you ordered. Whether to sit back and respectfully enjoy with some level of contemplation, or whether to quaff that ale like it's your birthday.
What is your favorite glass? Do you think it makes a difference? or do you prefer to drink from the bottle? Don't just take my word, go ahead and experiment or let me know what you think and what your experiences are in different regions or with different glasses.