Tactics for potions work, or they did before the most recent patch. I don't bother setting them anymore so I'm not sure if that's been broken since.
Get a sword and shield character, pump their strength so that they can wear the best armor you have, and set their talents to something like this -
Always use - Shield Defense
Always use - Threaten
Always use - Taunt
Always use - Precise Striking
Early on this will be all you need, along with those nice Warrior talents that boost damage...etc. Once you get the Blood Dragon armor equipped, your character (Alistair or your main) will be nearly unkillable while freeing up your allies to attack at will.
If you have Leliana, activate her Bard talent which boosts damage and attack (third one in the tree). If you don't have that unlocked, just use the first one (mana/stamina regen).
If you're very early in the game, focus on Shield Defense and Precise Striking. The last one is a must for any melee character, in my opinion. Pump Strength and Dexterity on level up. Really it's all about getting your Sword & Shield character properly set-up, once he/she is ready to go you'll breeze through most battles.
If you have a 2-handed character do NOT use Powerful Swings (it's bugged) and always try to have a maul equipped, mauls have a x1.25 Str modifier which is a sneaky bonus over the x1.10 of the blades/axes. And if you're up against enemies wearing decent armor, you'll do monster damage. I like to activate Indomitable, Precise Striking and use the Sunder talents since they hit twice during the animation, the damage is very good along with the other effects.
These are just basic tips, they can all be setup in the tactics screen which leaves you free to spend most of your time micro'ing your mage during battles.