| Imo the first thing that you'll want to look for is the availability of a certain DSLR system aka customer support. For example, Canon and Nikon have excellent support in any country because they're very well known, which makes it easier to find accessories and equipment. Other brands like Pentax and Sony might not be so.
Second, depending on what you're going to use your DSLR for, each system has it's own strength. If you're going for fast action photography, you might want to find a system that has excellent autofocusing ability like the Nikons, the Canons and Sony. If you're focusing on video capabilities go with the Canon/Sony. If you're looking for an affordable weather sealed DSLR go with the Pentax. And so on and so forth. Try researching into each system and know their pros and cons.
Third, depends on your budget because the price on lenses and equipments vary according to each system. Canons and Nikons are fairly well known so getting your hands on second hand eqs is easier and cheaper. The Pentax system relies heavily on old and 3rd party lenses so they also tend to be cheaper.
Finally, if you're looking for excellent image quality but hate having a bulky camera, go with the mirrorless system. They also feature interchangeable lenses and larger sensors than your point and shoot. The image quality of some mirrorless cameras can even rival that of a DSLR. The only downside is that most of them lack an optical viewfinder.
Gluck! :D