1. Do the human intro quests.
Once you've gotten through the initial starting zones for a human paladin, you'll receive a decent set of gear, your first talents, and enough cash to get started venturing into deeper territory. You should be thinking about your spec at this point; either ret or prot work well for new paladins.
The human intro zone will also reward you with items that you can use to advance in levels. For example, humans get a mace specialization that you might want to consider taking advantage of in your travels.
2. Research specs, or go ret for safety's sake.
Retribution, or "ret", is the best talent tree to spec into for leveling because it does the most damage. When questing, you want to be able to quickly kill mobs so you can complete quests faster. Holy spec is for healing, and prot mostly for tanking, though it also doubles as a decent (though not ideal) leveling spec.
Later on, at level 40, you can dual spec for healing or tanking and this way be able to instance with other players as part of your world of warcraft human paladin leveling guide.
3. Make sure to upgrade gear and glyphs.
Your glyphs are an essential part of getting the most from your spec. You should be glyphing crusader's strike and any other ret glyphs as part of your talent point spending. Consider glpyhs an essential part of leveling so you can do the most damage.
As you continue questing, you'll see iny our quest guide where to go to get new quests and level up. You should do instances where you can using the dungeon finder, as they give you a nice boost of XP, gear, and money. You'll also get necessary group experience if you decide to do endgame content later on.
Ultimately, the best world of warcraft human leveling guide is simple: do each quest, make sure you spec ret at first, and save money for a mount so you can get around quickly. Don't buy gear from vendors you see on your way around Azeroth; instead use the gear you get from quests.
Also, statwise, you should be looking at strength for a ret paladin, and stamina/str for a prot paladin. Holy paladins need intellect and spirit; caster plate gear, in essence. You'll need to examine each piece of loot as you receive it to make sure it's ideal for your spec as you level.