I generated a map via Interactive Visited Countries and I can see that I've a lot of ground to cover - literally!
1) Traveling companions
I'm not one to travel solo, partly due to security. I also like some company and camaraderie on my vacations. I suppose one day I should indulge in a solo trip but at the moment, it just seems like a better idea to travel with someone. However I do believe you should pick travel companions based on the nature of the holiday and their personality; beware the make or break holiday!
I am willing to spend more for the experience; there's no point traveling somewhere to stick to cheap options. I have a yardstick for different regions and I cross check with others to get a good gauge on the budget that I've calculated. I find myself paying attention to advertisements on holiday packages to get a feel on the expected cost. Also I'm sharper in checking out the fine print and the T&C for hotel/packages.
You don't want to squeeze too many things to meet the budget; similarly, you should try optimize the time you have. I always start with itineraries provided with Frommers; it's free and can be comprehensive, depending on the place you want to visit. Then I do my own research on the attractions I want to cover and the geography of these places with each other before I settle on an itinerary.
I set reasonable expectations for each trip. I ask myself: what do I expect to gain from this trip? What is the theme of the trip? History? Adventure? Relaxation? Once I set an expectation, I design my trip to meet that expectation. If I'm there for relaxation, I won't include energy-consuming activities unless it is practical to do so.