If a building is finished and you get the placing - roster, go with this building around your base. If a part of the roster turn red and there is no obstacle near, then there is a mine.
Discover Submarines
Select a gunboat or destroyer and move the cursor into the radarmap. If the cursor turns into a attack cursor, then there is a submarine.
Fast Building Of Vehicles
You need more than one warfactories for this. If a vehicle is almost finished, quickly change the primary building and start building the same type of vehicle. Both vehicles will be finished at the same time.
No More Silo's Needed
If your silo's start getting full, just build an expensive building. If the building is finished, cancel the building.
Press Control and see what happens
Pressing "CTRL" forces attack cursor.
Uses:
Well, first of all, you can use this trick when you want to attack objects that usually cannot be attacked upon by you e.g. rocks, trees or your own units, (you don't really wanna do that unless you get really sick after loosing battles over & over & really want to suicide).
But Two important uses that I figured out :
1) Select V2s/Tanks/RocketSoldiers/Grenadiers and CTRL+CLICKing a BRIDGE will force them to attack and Destroy the bridge (if possible) and thereby forcing the enemy to find another route, very useful when different Routes/Bridges lead to your base, & you want to concentrate on defending only few of them.
2) If a mine is dicovered ( how this is done is discussed on the same page ) you can desroy it by CTRL+CLICKing on the ground target .(This will definitely save lives of units that otherwise would've been used as BAIT etc. blah blah)