Selecting:

Photographers will send you an album of the photoshoot.  You will need to go through that photoshoot and start eliminating shots and getting that selection into about 4 to 6 shots.  More than that is overkill and overwhelming for most agents to work with.  

The best way to do it is for you to sort through the shots pulling images you like into a separate folder.  Take a step away.  Get yourself a coffee, review your casting, review your personal goals, take a walk have a zen moment, then go back again and sort through the images you set aside.  Make sure you have shots that cover your casting and examine them again weeding it down further.  Once you have it down to about 20 shots then you send the top selected to your agents and/or manger.  Ask them what their top few shots are or if there are any must have shots.   If you don't have an agent or manager to turn to you can ask family and friends, but keep in mind, unless they are real professionals in this business, their opinions don't actually offer you much more than a person to talk to about it.  Asking your photographer will be way more beneficial than family and friends if they do not have a firm real workable understanding of the business. 

What you should get and what you should request:

Typically photographers will give you a digital album (large size) of the full shoot that you can down load.  Most give you two to three free edits and will do additional edits for extra cash.  With the edits you should get them in both a printable large size and a small internet ready size.  You should ASK your photographer if they would not mind formatting the large images with formatting as well.  Meaning there is a clean simple boarder and your name in the lower right hand corner.