Quick passing-and-receiving is the core of the game IMO. Just don't dribble too much - the longest I keep the ball would be about 3 secs. at best. It's important to move your whole team forward with that, not only the center forward and the his sidemen.
Also, be quick with your player switching, try to follow the opponent (not your own co-players) and switch at the right time, the engine is a bit more refined in NGC98 so it hardly activates the wrong one. However, if it does, don't start mashing C because you will lose valuable seconds that would be better spent with a tackle to regain initiative.
45 degrees goal kicks work better than a frontal approach, that's for sure. Another approach would be the "near-corner" tactic, just move down (or up) to the opponent's corners and pass the ball into the goal zone for a goal kick attempt, this way you can also score a lot of head goals.
About the strongest teams, well, that's a bit subjective because it depends on your playing style. If you like fast teams with a good tech level, you'd prolly choose one of these:
Holland
Brazil
Germany
Sweden
Argentina
France
These have lower power and tech, but very good defense:
Poland
Norway
Switzerland
Denmark
Greece
These are very fast:
Czech Republic
South Africa
Guinea
Guatemala
These have a high tech level (good for all sorts of mean tricks):
Italy
Belgium
Wales
Bolivia
Iraq
Panama
These base their strats on power and the occasional unfair play:
Saudi Arabia
Thailand
Vietnam
Iran
Puerto Rico
Canada
Mexico
The remaining teams have some special combinations of skills that you won't find in others, like Colombia (powerful and good attack) or USA (powerful and very good defense), etc.
Read the Super Sidekicks 3 Countries List FAQ for more info (available on Gamefaqs).
