Don't Share a Room:  In our experience in running small group tours, it rarely works out well with travelers sharing rooms with someone they did not know before the trip.  People have different sleeping habits, they snore, they get up and go to bed at different times.  Some like the TV/radio/light on, some don't like the TV/radio/light off. We all have our own habits which may not seem quirky or bothersome to ourselves, but actually are quirky and bothersome to others.  In about 90% of the cases where travelers choose to room with another traveler, where they did not previously know that traveler, it turns out to be a negative experience. 

Ask Before You Go:  If traveling with a small group like those offered by The Traveling Professor, ask if there are other solo travelers on the tour.  You may feel uncomfortable if you would be joining a tour that only has couples, so you want to know beforehand if there are other solo travelers.   On our Traveling Professor small group tours, most have at least a few solo travelers.  Some of our tours are all solo travelers.

Don't Be Shy: Don't be afraid to share a table with other solo travelers.  When I used to travel completely alone, I liked to go to church dinners or to restaurants with community tables.  It was always a positive experience.

Get to Know Travelers Beforehand:  If going on a tour like one of The Traveling Professor's small group tours, ask if the emails of other solo travelers can be shared.  You could also go on a social media page of the group you are traveling with to introduce yourself and get to know other travelers.

Share Transportation:  If on a group tour, see if the company running that tour has other travelers arriving or departing the same time as you so you can share transportation to/from the airport.