I once said a BS is a simple machine. This is one of the dumbest things I have ever said. No disrespect to Alex but his video is a good starting point. If you are going to use a BS for simple cuts where precision is not critical it is not that difficult. If you are going to make complex cuts where precision is vital it becomes very complex.
Hank, on this forum. in one of his posts has a very good check list. I increased the font size and printed it. If I have not used the BS in a while I use Hanks check list.
Itturra Design in Jacksonville, Fl. is a great resource. They design and manufacture BS parts. His parts catalogue is also a text book and history book. Yes it leans toward Delta but you do not need to own a Delta BS to learn a lot from Mr. Iturra. Every time I have called his company he has answered the phone and been willing to help me and answer my questions.
There are a lot of high priced after market parts you can buy but until you have the variables in a BS correct there is a good chance you could be wasting your money.
A word of caution, there are some BS videos on utube where some people do some really crazy things which could cause serious injuries.