A few tactics then:
Cognitive:
1. Guys with medium or heavy armor, holy symbols and simple weapons are generally clerics.
2. Guys with light armor and light (or finessable) weapons are generally rogues. Don't let them flank you or you'll regret it. OTOH, they tend to go down quickly and are consequently good cleave bait.
3. Guys or girls in skimpy, nonportective costumes with only a dagger, quarterstaff are generally wizards. If you can get to them without taking a pounding from AoOs, you want to get up close and personal with them and power attack them to death (generally, they have low AC and low hp--if they're polymorphed into lizardfolk form, they don't have low AC so don't power attack but they've still got low hp so you can quickly cleave into the rogue).
4. Guys wearing heavy armor and using martial or exotic weapons are often fighters. Guys wearing light armor and using non-finessable weapons are generally multiclased fighters or barbarians. They're able to both dish it out and take it which means you can't afford to ignore them and you can't afford to focus on them (the cleric will just heal them while everyone else pounds on you). You might try disarming them or sundering their weapon (especially if you have the requisite feats). That will reduce their hitting power without taking too many of your attacks away from squishies like the rogue.
5. If you see someone raging, power attack. Barbarians typically have rather poor ACs.
In general, if you're a single fighter up against a party of PCs, you're hosed. If you're going to win, you need to open up on them very quickly and very hard, and take down one or more of them in the first couple of rounds. If the wizard is bleeding and the cleric is spending all his time healing the rogue to keep him alive, your odds are much better.
Really, though, you'll want magic. Things like a potion of Blink or Displacement that give your foes a 50% miss chance will go a long way towards helping you out--especially if combined with a high AC.
Also, if you're facing four characters, you'll want reach too. A reach weapon like a guisarme or spiked chain with combat reflexes and improved trip can really help to even the odds (since you will often be able to stop one or more enemies from closing with you). Adding Spring Attack would let you move, stick the rogue (who tumbles through to avoid the AoO and thus can't easily be stopped) and move to threaten both spellcasters (forcing them to cast defensively).