Thank you, /u/jrs12, for a perfect post and perfect suggestions! Yes, exactly all of that! :)

Very often your wait time will depend on three things:
1. how long it takes you to complete the entire application.
2. how long it takes the school to do an assessment and complete the work on their end.
3. whether or not that school has a good dog match for you (almost most important of all! you'll get nowhere if you say only a female German Shepherd pure bred with blue eyes. guaranteed)

Get your O&M skills down pat and have at least 3-4 routes with meaning and purpose. You must have a NEED to work a young dog, not simply a desire for a companion to walk you to your mailbox and back.

The dog will not keep you safe from scary people.

German Shepherds are not as easily bred with similar temperament and personalities as labs. Do not expect a school to have a huge supply of them (aside from Fidelco). Same goes for goldens.

Stay in touch but don't annoy your admissions person by calling over and over and over and over again.

Research and actually speak with working guide teams. This is critical to understanding the needs of a team and will better help you figure out if this is a good move for you.

A dog is a lifestyle choice and you must be financially able to care for it. Lifestyle because dogs are dogs and need certain things, and money cause dogs can be expensive little buggers. But we still love them.

Don't get frustrated if you're not picked for a class. Listen to the feedback and try to improve. Most schools do want you unless you're a bag of dicks and are hateful to everyone. Don't be that guy/gal. Just keep trying to work on your stuff and reapply later.

Source: I work at a major GD school.

O&M instructor here. Make sure your mobility skills are on point. Lack of mobility skills is a major reason for being denied. If you have a preference in breed or gender of dog it will take longer to find a match as well. Also, I would only suggest getting a dog from a school with a good reputation. Don't go with a school no one has ever heard of. You're going to want back up and someone to turn to if you have questions once you get your first dog. Some schools are better at that than others.

The amount of time you'll be waiting really depends on which guide dog program you want to attend, but it's usually about 3 months after your application is accepted assuming everything goes well. Unfortunately I can't really tell you anything special to expect since I don't have a guide dog myself, though I do hope to get one in the future after I figure a few things out. I've done a lot of research though.