I been thinking about this for years and was always to sub-conscience to ask anyone what they do when they are travelling alone. As person who is on the road about 90 days a year I spend a lot time dining alone. I could spend time with clients at dinner, but I prefer to turn off work mode after hours. One thing I have done in the past that makes me feel more comfortable is to book at table for 4 and say the rest of the party is coming. Then after 15 minutes or more go ahead in order and later say the rest of the party will not be coming. I have found the staff is more friendly towards me for being "stood up" I always tip well (I am on an expense account after all). I tip the host and waiter when I return to the restaurant a lot of times the staff remember me and I feel less uncomfortable.