If your problem is specifically coming in second place to solos, then I recommend looking into stalemate lines a bit, at least enough to get a sense for which big powers are dangerous and which are not. For example, England essentially cannot win the game without reaching one of Tunis, Venice, Vienna, Warsaw, or Moscow. A 10-center England that has removed the entire French fleet and has taken Tunis is therefore probably more dangerous than a 15-center England that has a fleet in St. Petersburg, most of France and Germany, but would have to contend with a strong Austria on land and a strong fleet power in the Med which is knocking on the doors of Marseilles.
One other important thing to remember, though: balance of power is something to always be aware of, but your goal is not to keep the game in balance, but rather to create conditions under which it is correct for you to grow (meaning, conditions where you are capable of growing and where growing helps you rather than hurts you). When I see another player on the board that is about to grow, my first instinct is not to stop their growth, but rather to see if I can find a way to benefit from it. I'll give you an example:
Imagine playing England and seeing a big, scary Russia on 8 centers in 1902. Yes, one option is fighting over Scandinavia and reducing Russia. But if I'm successful, then I might get one center out of it; Germany will probably get more, and if we do reduce Russia a bit, we're back to a 7-player game where anything can happen. That's not a bad Plan B, of course, so negotiating a Western Triple that lets Germany and I push back Russia in the north makes sense.
But if the setup is right, I would be much more inclined to let Germany swing East and help fight Russia *to a draw*, while I stab a vulnerable France instead of continuing with the Western Triple. Then, Germany is faced with the choice of letting me grow or letting Russia grow, and will probably stick with the war he's already in, since he's already in position and since, ultimately, he'd rather see me grow than Russia while Russia is already on 8 and I'm growing to 8-9. In other words, Plan A is using Russian growth to negotiate my way into conditions where I get to grow and catch up, and rolling things back towards equality is Plan B.