What are some techniques to avoid annoying the travel mate?

Prepare your trip together before departure.

I don't mean planning every detail such as hotel booking or what to do at each place and the exact dates of moving from one place to the other.

I mean discuss together about how you imagine the trip: budget or luxury, need one shower per day or once a week, travel light with time spent washing clothes or having a big backpack, visit as many places as possible or stay several days at one place, wake up early or prefer nightlife...

Be open to your mate's opinions and then make compromises. You even can choose to make separate subtrips and meet again some days after: it opens the opportunity to chat about what you experienced when alone.

You need to find out before travelling what sort of a traveller or experience your travel mate has. You may be okay with living in the cheapest hostel you can get, but your mate might not. Too often it's easy when one of the partners has more travelling experience that the other person will leave the planning up to you and then not be happy about a different level of comfort. It's important when travelling for a week or longer to also not always eat meals with each other or go to the same places...but at the same time it is important to do some activities together to keep everyone happy.

I agree with all previous answers, but I want to add another important problem that I recently encountered and which I think should be discussed before a big trip.

I think before going to a big trip with a travel mate one should also talk about the safety level that each traveler expects. The subjective safety can vary heavily and if you do not agree on a common "safety range" it can lead to problem.

For example if one of two travelers has to go out all night in very dark streets with dodgy types and he does not feel well with that this can lead to problem sooner or later.

Very good question! I lost my share of (good) friends because of travel together for a longer period. As @hippitrail said traveling is a great relationship validator!

Some things I can suggest:

• Do short trips before going on a long trip
• Don't fall in love while traveling. This is definitely a deal breaker!
• Agree on whether or not you accept other travel companions or prefer to stick to each other.
• If thing grow sour, accept it, split up and allow a cool down period.