This sometimes annoys people I travel with when I shout at them because we need to hurry up and catch the 10.11 bus because the 10.14 bus would completely ruin our schedule. But they appreciate it when we save time and stress because we know exactly where to go, or when we stay at a great hostel in a convenient location for a good price.
Plan In Advance
I am a firm believer that if you plan your trip in advance, it will ultimately go much more smoothly and the experience will be more enjoyable because you will be saving time and money while getting the absolute best out of your trip.
However, I will also concede that plans should be flexible, and if you get delayed and can't catch a certain bus or visit a certain museum, all is not lost. Stressing because everything didn't go 100% as planned will mean you won't have a good time either, so relax!
Know Where You're Going
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Getting lost, for me anyway, is really stressful. It means you waste a lot of time that could have been spent doing something else. That's not to say that you won't have an adventure and come across some hidden gems off the tourist route, but especially if you're travelling alone I think it's vital you know exactly where you're going.
Money, money, money
I'm a total cheapo, which you may or may not have noticed. So when looking for a hostel, I have to reconcile the following: price, location and safety. If there's a big group safety becomes slightly less important, which leaves price and location.
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Regarding food, it's obvious that restaurants and cafés on the main tourist strips are going to be much more expensive. This can't always be avoided, but try not to make yourself a victim either. If you want to check out some places in advance, reading through Trip Advisor recent reviews is always a help. But beware of those restaurants marked 5 stars that have only been reviewed by six people, as opposed to the restaurants marked 4 stars reviewed by 3,000 people.
There are such things as free meals. . .well maybe
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As a general rule, most major cities have free walking tours (well they expect a tip, but since you won't ever see them again that is entirely up to you. . .) and there are usually places where you can get a good view of the city for free - if you know where to look.
Also, be wary of paying entrance fees into places. Do you really need to go inside? Is the national gallery something you genuinely have an interest in, or is it just a 'must see' attraction you found on a list? Think it over before handing out the admission fee.
Take a chill pill
Well, not an actual pill. But you should relax and have a good time, it's a holiday after all!