I tend to not worry too much about player tactics, though I do approach each major combat encounter with the thought of, “If I were the group, what would I do here?”
Of course, 80% of the time they do something else.
Most of the time, I am concerned about monster tactics. But, I tend to base that on the monster’s intelligence and ability. In 4E, the goblins are going to attempt to take advantage of goblin tactics and flanking, while hobgoblins work best when sticking together with the other hobgoblins and so on.
For the players, I am happy if they do the simple things to help each other out – using a power or ability to push or slide a monster out of a position adjacent to another PC, the shaman using his healing spirit to its best ability, the bard using his ritual to boost the party speed when they know a combat is coming, etc. I do not expect more than that, though I have rewarded good strategy with an easier encounter.
Between sessions, I may make a suggestion or two based on a character’s ability, “As a fighter, your character is aware of the combat situation well enough to know that if you did at-will ability X instead of your normal ability Y, you would be more effective against the foes you expect to face next session” I only do stuff like that if I felt a player missed something in game and we forgot to mention it at the table, as these things can be easy to forget in the heat of the moment.
However, I will also add at the end, if the players are high enough level and are facing groups of similar foes (i.e., the followers of the evil god of slavery and tyranny), the bad guys will adjust their tactics if the players do the same thing every time out.
In my last campaign (3.5E), we had a big group of players and they generally had the same overall tactics – the dwarf fighter and goliath barbarian would charge into combat at the nearest foes, the elf paladin of freedom/champion of Corellon would engage the bad guy with the best melee ability, as he had an amazingly high AC, the sorcerer would hurl acid-based spells, the rogue would attempt to flank with the elf paladin, etc. They were engaged in attempting to stop the followers of the aforementioned evil god of slavery and tyranny (as opposed to the good god of slavery and tyranny).
As they got higher in level and knew a combat was coming, they would decide which buffing spells to cast prior to combat, which is pretty tactical in thinking. (Somebody on here wrote that high level spellcasters spent a lot of time buffing & debuffing in high level combats in 3.5)
Once the party gained in level and reputation, though, the bad guys who followed this evil deity were able to adjust some of their tactics and knew they had to hit the elf with Area of Effect spells instead of engaging him in melee (his touch AC was also high due to high Dodge bonuses), while the dwarf and goliath were vulnerable to ranged touch attacks, and the party psion was deadly with his short-range Crystal Shard, and so on.
Granted, I did not let that affect how a signature foe would attack them, for example, the drow duskblade that had survived four previous encounters with the party still rushed to engage the elf in melee, as she was sort of the mirror opposite to the paladin of freedom.