I'm preparing for a 3.5e game, and I wanted to be a fighter or a marshal, but I also want to be able to use the maneuvers for martial classes. It does not say that one must be a swordsage, warblade, or crusader to use these actions, but it also does not say that one has to be that either. Please help!
No, but you have to learn maneuvers to be able to use them.
The classes presented in Tome of Battle learn maneuvers automatically as they gain levels, but no other class does. The crusader, warblade, and swordsage are also the only classes who gain a mechanic for recharging their maneuvers during a fight.
Other classes can learn maneuvers by taking the
Generally speaking, if you want to use the maneuvers from Tome of Battle, you should make a character of one of the maneuver-using classes. A fighter who uses his bonus feats to pick up maneuvers is generally going to be weaker than a warblade (in many ways, the warblade is intended to replace the fighter, which is considerably weaker than the other PHB classes unless built just right).