I just want some tips or a tutorial on how to use a shield/sword combination successfully. I usually go battle/mage but crafted a daedric shield and would love to use it. I did use it on one enemy but after one block my shield went down. Do I press the shield button everytime he attacks or hold it.

Any tips would be nice

You hold it, if they power attack it goes down, depending on your levels you can recover quicker than they do and swing or bring the shield back up or they recover first and attack.

There's no real tactics involved if they are swinging fast bring the shield up, if they are going for a power attack either swing first or back up, or see above.

If your a higher level and the enemy cant really hurt you stand there with your shield up to level it.

When you level up enough you can use shield bash to disrupt/hurt them.

PRO TIP: Press the attack button + forward button until it dies.

I need to go practice this more, but what I do is hold up my shield when I go into combat, then I do a power bash, then I do a standing power attack, then repeat (my shield guy has stamina up the wazoo). So, hold LT, then hold RT, let go of LT, hold RT, let go of RT, hold LT again. Honestly I think there is more to it but I need to leave my bow at home and just practice shield for a while.

Actually there is a book in the game itself that goes into decent detail on how to use one I would say its named shield wall or similar but I may be confusing it with something else.

When you get the slow time perk it becomes less of a hassle with power attacks since you could move out of the way or attack/bash them back.

So just hold the shield up because the enemy I tried it on was adual wield and he did manage to lower my shield multiple times in combat before I finished him off

Pretty much, if you won you were doing it right. As you progress in all skills you'll be able to choose some perks to improve it. They always have a shot at lowering your shield though, it was either that or just let you walk behind a tank. Shield bash comes in handy against groups, later on.

Just block again I guess? Or bash him then hit with a couple regular swings. You might not want to constantly power attack because your stamina will run out, and then your blocking will be total crap.

My Nord Warrior uses Mace+Shield alot, and even during a Giant's power attack, his shield doesn't lower. Could be because he has 100 Block, or also the "Tower of Strength" perk in Heavy Armor, which makes him stagger 50% less. That perk is awesome, i can take a full "Fus Ro Dah" to the face from a Draugr Deathlord, and i barely flinch.

Go here to get more info: http://www.uesp.net/wiki/Skyrim:Block

Also, you should have perks in Block.

Good luck.