my biggest question is when you record yourself and do your voices for your "samples" do you make up what your going to say or do take things out of books or famous quotes from games,books,films etcs?
First thing you should do before recording samples is to write out what you're going to say and become familiar enough with it that you can say it naturally. Some pro's can cold read and nail the inflection and characterization... but someone who is learning and even many professionals, should take the time to get this stuff down before you start recording. At the very least by reading it aloud once or twice first. Some phrasing may read smoothly enough, but the specific phonetics trip you up every time.
Pick 'normal' phrases and sentences. Quotes from films and books can work... but often the things that people remember are self-contained. What you really want to be able to do with voiceovers is converse, even though you're not necessarily recording the question or the response to your answer (this may be done by another talent), your sentence has to fit. Jotting down the dialogue from a cutscene in the game might be a good start. You can also write similar fantasy setting material ("Be ready with your spells the moment the orcs come over the rise!") ... or replace orc with darkspawn...
This shows that you can do setting style dialogue. You might also consider doing this line in a couple different ways... once as a grizzled veteran warrior who leads the unit, once as the panicky priest who is afraid that you're about to be overrun, maybe once as the kindly old mage who taunt you everything about causing orcs to explode. This shows that not only can you do setting specific dialogue, you have a range of vocal quality and inflection that will support roles of certain types.
Always remember that while being able to mimic bits and pieces of this character or that actor is good, being able to say things in that voice that the original never said is far better. If you're being the voice for anything other than a one shot extra, you may have to be able to remember and reproduce that same voice consistently for hundreds and thousands of lines.
Finally... make sure when you sit down (though I've always preferred to stand for vocal work, far easier to do if you can engage your whole body) to do recordings you've got somewhere good to do them. The last thing you want to do is send off a bunch of brilliant samples to someone that have an awful background level from your air conditioner or computer fans, or any number of other sounds that can take tons of work to clean out of a vocal track.