Well, to be perfectly frank, anonymous, there are tests designed to help match a trainer with a partner, but not many of them are all that accurate. Besides, pokémon are living beings with individual personalities, so it could very well be that even if you found a species you resonated with, you may not get along well with the individual paired up with you as your starter. Conversely, on the other hand, you may find that a pokémon you never would have dreamed of training ends up being your closest companion. It’s all-around a bit of a gamble.
My best advice is actually do continue doing your own research. Get to know as many species of pokémon as you can by simply reading about them in standard textbooks or on the internet. Ask trainers questions about specific pokémon or interact with them at your nearest shelter, pokémon center, or professor’s laboratory. Consider even taking an apprenticeship or internship at one of these locations so you have plenty of opportunity to get to know individuals.
But above all else, be patient. Finding the right partner is rarely as easy as television and movies will have you believe. You’ll find one you resonate with, I assure you, but it will take a lot of research, meditation, and interaction to do so. Then, when you’re on the road with a partner, don’t worry too much about which pokémon will be perfect additions to your team. Part of training is getting to know each pokémon you acquire and figure out from there how to bring out their individual strengths and weaknesses. The act of training in itself will help strengthen your bond with a pokémon, regardless of what it is.
If, however, you mean you don’t have a particular favorite, I wouldn’t worry about this either. Some people have specific favorites, yes, but others may like a wide variety of pokémon. It’s actually a great thing to be open-minded about pokémon, as every one of them has their merits.
In any case, best of luck with finding your partner, anonymous!
The Pokédex According to Bill 