RCCL (amazing quality and service and clientele) can be booked on line, further in advance better deal...or last minute. Their website is actually quite good as well. Personally for first time cruisers, Id say ask people you know as far as which cruise line,
they vary greatly!!! You can also go the
travel agent route...Have you been on cruisecritic dot com? A GREAT wealth of information (the dis for cruising

) worlds of info, great forums and so much info so ask away.
We have cruised RCCL and I must say, it is truly first rate. My only cruise hint...for first timers, be prepared to spend more than just the cruise...it adds up (drinks, bingo, activities off shore) AND middle of boat up and across are steadyest....we had no issues but cruised in spring not during a rough season....
Rccl also has a credit card and amazing promos, we got lots of cruise money to spend on the ship and we went balcony, I would not do without it....Some say you are not in your room, well, we LOVED going to bed at night and waking up to see a "new experience" in the horizon just waiting for us, drinks and choc strawberries at night looking at the bluest water ...breakfast on the morning or just a cup of coffee....a WONDERFUL, not to be missed experience! Jr Suites are also great!!!
Good Luck choosing.....My personal opinion is that these new HUGE HUGE ships, rccl included are to keep you on board, more sea days rather than visiting and that is a shame...yes, THEY make money, but you LOSE on seeing/doing more. There are TONS to do on the ship but thats not really our thing,,,,though, yes we skated, rock climbed, basketball..inline skate, swim, Johnny Rockets "show" mini golf all while on ship...the list on RCCL goes on and on.... rccl is a

Oh and their ships have a HUGE central promenade that runs the entire ship on one floor....has stores, bars, it is wonderful..... each night we'd visit another place, have a drink, relax...so much FUN FUN FUN.........
Good Luck deciding...research away................Oh the memories.......