Elder Scrolls V: Skyrim - Guide to Combat Skills and Perks
Smithing
This is the easiest skill tree to explain. If you wear heavy armor go to the right, if you wear light armor go to the left, and if you enchant your armor then get the perk in the middle. WARNING: If you are going to the heavy armor side, note that daedric gives a bigger armor bonus than dragon plate but if you get the dragon perk you can earn a lot of money from killing one dragon.
Heavy Armor
For this tree it is suggested that you go up the right side and get all of the skills that increase the rating of heavy armor and allow it to reflect damage. The left side is completely optional but if you wield weapons and are careful when you fall then it is a waste of perks. Heavy armor is much better than light armor because instead of avoiding damage as the final perk you reflect it onto your enemies. You also want to make sure that you level juggernaut up all of the way so that it can stack, doubling your armor rating (plus whatever else was increased on the tree).
Block
This skill is not only useable when wielding a shield, but also when you when you are only wielding a weapon. This skill tree is extremely easy to explain as well. If you use a shield all of the perks can benefit while if do not wield a shield only the the right side of the constellation will benefit you. The different sides are split up based on what type of blocker you are; right is offensive and left is defensive.
Two-Handed
The beginning of the skill tree branches out into four different places, basically making you choose which two-handed weapon you want to specialize in. Limbsplitter is for axes, deep wounds is for swords, skullcrusher is for maces, and champion's stance is for any two-handed weapon. Once you begin going up the tree you realize that there is only one choice past a specialization and that is whether you charge your enemy (great critical charge), or just fight them when you get to them (devastating blow).
One-Handed
The beginning of the skill tree branches out into five different places, basically making you choose which one-handed weapon you want to specialize in and whether or not you wish to dual wield. Hack and slash is for axes, bladesman is for swords, bone breaker is for maces, dule furry is for duel wielders, and fighting stance is for any one-handed weapon. Once you begin going up the tree you realize that there is only one choice past a specialization and that is whether you charge your enemy (critical charge), or just fight them when you get to them (savage strike).
Archery
The archery skill tree can (like most skill trees) be cut in two sides. The left side is for sniper type bowman and the right side is for ranger (medium to close-range) type bowman. There are not many choices beyond that but realize that all of the bow skills can benefit bowman if you use them wisely no matter what your play style is.