Beadz, there are three ways that I suggest you use to find suitable places to stay whilst on the road.
1) talk to other travellers you meet on the road.
2) take a guidebook.
3) ask as you go for specific recommendations on this travel board but on the appropriate branches. And use the search engines but good luck with that because I don't know if they work any more.
The best approach is to use a combination of all three of the above or at least two of the above.
At this stage of your planning, however, where you are going to stay should be the least of your concerns.
I suggest at this stage, saving the money should be your main priority.
Second for immediate research borrow some guidebooks from your library. You don't need to buy the ones you want for the journey until not too long before you leave so that they are up to date. It might be easiest also for you to buy one for africa, one for south east asia and one for south America and buy them as you go rather than all before you leave. If you need more, buy them on the road and consider even buying secondhand from other travellers. Or do the new thing and buy just the sections that you need from online.
Guide books and i would recommend LP or if you are american, Footprints, can give you help with everything you need to know about for overseas travel. They do make plenty of mistakes and are always a little bit out of date) so don't treat is like a bible. There are however quite a few things that they are very very good about.
1. guidance about respecting local customs, looking after your health, your safety. You would be well advised to be very familiar with these aspects.
You should probably try to buy your first flight ticket about six months in advance to take advantage of the lowest prices. Ditto if you are buying an rtw.
If you want more advice about buying rtw tickets, take a look at lonelyplanet's The Gap Year book. There's a lot of other good help in their also and you might even consider buying a copy now rather than later. You could also just borrow a copy from the library too.