Your choice of billiards table will probably be dictated by the amount of space that you have available in your house.
Billiards covers the sports of pool, billiards, and snooker, so here's a quick run-through of the sizes of table that are available:
Pool - Most of us will probably want to buy a pool table but may not realise that there isn't a standardised size for pool tables. You can get smaller ones which are 7 foot long by 3.5 feet wide, or you can go for the larger 9 foot by 4.5 foot tables. From a playing perspective, I much prefer the larger table. However, from a space perspective there's no way I could fit the 9 foot table in my house unless I put it in the centre of the living room - my fiancee probably wouldn't be impressed!
Billiards: The peculiar cue sport of billiards can be played either on a table with pockets or on a specialist table without pockets. I think most people who are in the market for a billiards table will opt for a pool table and will play billiards as well as pool on it. However, if you want the pocketless billiards table, then they're 10 feet by 5 feet, so slightly larger than a pool table.
Snooker: A full-sized snooker table measures a whopping 12 feet by 6 feet. As well as requiring a lot of space, they are also very expensive, and these two factors conspire to mean that they are generally only the preserve of the very rich. However, you can buy smaller snooker tables. The best birthday present I ever received as a kid was when my parents bought by a 6 feet by 3 feet snooker table. I was able to also play pool on it, and its small size meant that it was fairly easy to accommodate within the house. Note: you can also get even smaller snooker tables aimed at small kids. I started with one of these but quickly outgrew it.
Having outlined the types and size of tables available, you probably have a good idea of the type of table that you'd like. The next step is to check out the prices. Try visiting a few retail stores that sell tables and also look online. As well as price, another thing that I'd suggest you look at is whether the table comes with folding or detachable legs. Most standard pool tables, (i.e. like the ones in pubs) don't. This creates a slight difficulty if you want flexibility in the use of the room that you've allocated for your table. If you can get one with folding legs or detachable legs, then when you're not using the table the room can be used for other purposes.
My experience is that you should look for a table of about 6 feet or 7 feet in length. This is a size that is manageable within most residential houses and won't set you back too much in the pocket. I also like tables that have folding or detachable legs, so that the table can be put away if the room needs to be turned into a spare bedroom, etc. I'd also recommend that when you buy your table, you try to get hold of both pool and snooker balls. You may have a preference for one sport over the other but it's fun to mix it up sometimes!