Book flights early and directly with the carrier. If you do go through a discounter, be sure that the e-confirmation number is directly from the carrier. Verify it online to avoid nasty surprises at check-in.
Book rooms directly also. I’ve witnessed a number of travelers try to check in to a hotel, only to find that the discounter’s reservation was never received. Again, if you go through a discounter, call the LOCAL hotel number and verify your reservation.
Vegas is a destination that one can typically benefit by using one of the larger travel agencies that benefit by block and group rate discounts.