Here is some tactical advice for new players:
1. It's pretty rare that a tactical decision is needed! Based on diplomacy talks, the right moves should either be obvious, or you should be facing a difficult strategic decision (attack or not attack for example), not tactical.
2. Another way to avoid tough tactical choices is to worry about position more than the centers. Spring is for position, Fall is for taking SCs. Always think at least until the end of the year.
3. If you do end up facing a tactical decision because you are openly fighting another country, the first thing you should do is see which moves the opposite power HAS to do. Once one move is obvious, the rest should fit in like dominoes. Once you figure out the possibilities for your opponent's moves, just counter them! A good thing to do is to not even try to think abotu your own moves until you figure out what your opponent is likely to do.
Note: the above advice only works against new weak players. If your opponent has more than 500

... well then you probably don't need my advice. Well one thing for intermediate players - take a look at the history of the moves for that player - does he liek to take risks in spring or fall? Does he anticipate his opponent's moves or just try to power through? Does he like to do tricky moves like weird convoys, or double attacks on his own unit for protection or supporting the enemy self bounce? This should help you understand what he might do.