Most Enemies have a pattern in which they attack. Use the shield to block until you can work out which directions you need to dodge next time. Some enemy attacks cannot be parried and are unblockable, so if you see the Dark Knight bashing his Aegis shield, get ready to dodge left side and stab him in the stomach when there's a window for you to (tap circle).
Some enemies may have an ailment icon next to the offensive upon inspection. If it shows up with one, it means the enemy can cut right through your block and applying the ailment if it uses a power attack, even though the raw damage is not applied. Try to dodge or parry the strikes of their weapons. A good way to counteract this is to check if your shield has resistances against the element an enemy is attacking with. For instance, if your shield has a darkness resistance, it can safely block power attacks of enemies using darkness without applying any damage and cutting off your shield block. It's perfectly fine to block the attacks of the body itself (if they're not charging or power attacks), or if the strike looks particularly relaxed, quick and controlled (e.g. a simple swipe, no spin attack or twin bladed enemies attacking with both blades), as the effect is not applied unless the enemy makes an actual power attack with the weapon.
You have a shield for a reason, but that number over your handy shield icon means it won't last forever in any one fight. Block the attacks that can't be parried (hand strikes, feet stomps, head butt, etc.) or any weapon strikes. Each block (successful or not) will damage the strength of your shield until it breaks. Some enemies' attacks, particularly those of larger enemies will reduce more of your shield strength than others. Shield bashes and other power attacks, however can cut right through your shield and hurt you just as if you didn't bother to avoid the attack at all, so if you see that big troll about to jump on you, you're in hot water if you think that slab of steel is going to be strong enough to bruise his rear when it hits the ground. Once the shield is broken, it stays so until the fight is over or you repair it with a shield spell during the fight. A broken shield means you will have to resort to parrying or dodging for the remainder of the fight if you do not have a magic ring that can cast a shield spell.
Magic is a powerful aspect in almost any scenario, and can assist you in a handful of fights. It can help you to kill an enemy by releasing an elemental outburst to harm them (if they're not resistant to a particular element, that is), or by enveloping you in a graceful explosion of shield repair or healing magic. Magic (by the top right) is filled gradually as energy in the air is charged by you two immature children (player and enemy) slapping each other with rather lethal grey coloured paper swords, literally to the death. Once the magic circle is fully charged, tap the magic icon to see all available magic runes for drawing. Draw a rough outline of the rune that contains the magic you want to use. You can be cut off from a magic cast by an enemy strike, so draw it out quickly. It's not a bad idea to make a poorly drawn rune as the magic will still be cast with no reduction in magical potency, so a U or an upside down L is absolutely fine in a pinch to cast heal or ice respectively, especially if you got an enemy sword strike cutting you off to worry about.
Once an enemy attacks, it will continue in a particular pattern until the attack sequence is finished. The last hit of an attack pattern is swung, and the enemy returns to a regular stance if it successfully hits you or just hits thin air. During an attack pattern, the enemy has a chance to be cut off and recoil, opening him up for attack. This can be achieved by Breaks, which can come in Block, Parry and Dodge breaks. Block breaks are common and provide a small window for you to hit the enemy. Dodge breaks slow game movement down slightly as either an opportunity for stabbing or just striking opens, but the enemy can recover faster from a Dodge break than a Block break. Parry breaks are riskier but provide a larger window of attack allowing you to connect with more weapon strikes than other breaks. Sometimes parries end up with a scenario with the weapons of both you and the enemy pressing against each other. The enemy will try to push you off balance and open you up for a quick attack, so push him off balance by rapidly tapping until he is stunned. The amount of hits available before an enemy reorientates his bearings is highlighted with a number of exclamation marks, next to the Attack Break notification. More exclamation marks mean the enemy is off balance for longer, and more hits can connect before your attacks are blocked. If your last "HIT" icon is one that comes with an exclamation mark ("HIT!"), it means you should stop your right arm assault immediately and re-ready yourself to block, dodge or parry before another break is available.