You might well want a travelling companion. You might not, but apart from the companionship aspect it's useful for sharing hotel bills, for example.
Take a decent camera.
Try as much as possible of the local food and drink. That's another area where you might need to keep an eye on your expenditure, particularly in the West; my opinion is that you should try to eat as well as possible, and that you don't go on holiday just to starve on bread and water, but at the same time eating in restaurants all the time isn't possible for most people. Likewise, and don't think I'm lecturing (perhaps this doesn't apply to you, but there might be other people reading this), don't go and get blindingly drunk too often (in some countries this might be rather hard!). After all, you're going on holiday to see the world, not to nurse a hangover.
As for languages, it's probably good to know at least a few words of the local lingo, especially if you're going to be there for any length of time. But if you do end up relying entirely on English (I'm assuming your native language is English) in most of the countries, don't feel too guilty about it; no one can learn every language and there are very few people who speak even two perfectly. (For that matter, I suppose it could be argued that there are very few people who speak even one perfectly....)
As I mentioned above, do ask local people for tips about where to go and what to do.
That's just about all I can think of for the moment; if I come up with anything more I'll add it. Sorry if it's been too much to take in; I hope I've touched on most of what you were asking about. No doubt there are others who could add information as well, and I hope they do, and if anything I've written is wrong, I hope someone corrects it!
It's a great idea, and I hope it comes off. If you end up coming to the conclusion that it might be too expensive travelling all the way around the world (I don't know your financial situation, or how long you plan to take on this escapade), there's no harm in choosing a small part and exploring that. It's not out of the question that you could get a job abroad, but that's a different matter.
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I was reading below about a guy who travelled europe on cheap flights, and its quite inspiring for me.
I would like to travel the world, in no specific order, maybe completely at random, based on cheap flights available at each point. I would like to do this for maybe a year, or maybe longer.
I am totally inexperienced here, I have travelled to a few european cities, but that is all, and know I will be out of my depth here!
Has anyone any tip, links, ideas, or anything for me? I am thinking of leaving in the autumn.
I am quite interested in how people communicate when abroad, I use the net alot, and would very much like to use it abroad to keep in contact/find info etc, so any info on service providers etc in other contries would be appreciated!