When buying plane tickets, sometimes it is best to search for flights in the middle of the night to get the most affordable prices. 

Pay for luggage ahead of time because paying for it at the airport will be much more expensive. 

Hop on - hop off buses are a nice activity, however, it would be cheaper to buy tickets for public transport and tour around similar to what locals do. It could save you more than 20 dollars. Also, if you do want a guide, then there are free walking tours that are available in the center. 

Research the country that you are planning on going to before traveling there. It's important to check laws, rules, and the news to see if there is anything happening. 

It's a good idea to learn some basic phrases in the language that is mostly spoken in the country you are going to. If you can't seem to grasp the language, then make sure you have an offline translator ready. 

Make sure your documents are updated, prepared properly, and not messed up in any way. This includes damages, rips, and also check the expiration dates. 

Make sure you know what the currency is in the country you are going to. Also check to see how you are going to get money (ATM, Moneygram, etc) 

Check if your card can be used in the country because some countries have closed currency and won't allow your card to process transactions.

Be careful of pickpockets, crime, and scammers which includes fake taxi drivers.  

Try to arrive to a new country in the daytime. This provides you with more security and you can see your surroundings.