Druid is relatively easy to build, though you have to consider a few things.
First: the Druid is basically a jack of all trades, because it can do a LOT of things. It can heal, it can blast, it can do melee well (because of Wild Shape), it's one of the only two Pet classes in-game, and it does summoning phenomenally well (it has Summon Nature's Ally automatically added to their list). They can do each pretty well: they can heal, but not at first (they can do it well at 5th level, as they can complement Cure X Wounds spells with Vigor); they can blast pretty well (particularly at late game, when you can turn into Elementals), their melee can be focused into high attack and speed (Wolf Form) or proper defense (Bear Form), their pet is pretty strong, and they get a large amount of summoned creatures.
Race-wise, any class that doesn't provide a penalty to Constitution is a good race. Don't choose Warforged, because they get a penalty to Wisdom, which is their main stat. Half-Orcs and Dwarves do well, as Charisma is always a dump stat for Druids (aside from Wild Empathy, but you'll get a decent DC as you go on) and they provide vital stats for them (Strength and Constitution); Humans are always good by default because of their bonus feat choice.
You should define at first how you'll build the Druid: do you think of it more as a blaster, or as a gish? Blasters should build for Season's Herald, probably focusing on Fire or Cold spells for when they get their Elemental Forms (Cold spells let your Winter Wolf form work properly, but Druids get slightly more Fire spells); note that you can cast spells while Wildshaped (i.e. they get Natural Spell innately), so remain transformed at all times. Gishes should build for Nature's Warrior, focusing on one of the two forms (most people choose Wolf, BTW).
As a gishy type, get all buffing spells (Barkskin, Resist Energy/Protection from Elements), choose what kind of melee you intend to be (either DD or tank), and get the enhancements that boost those (those for DD tend to incline towards Bluff; tanking enhancements focus on Intimidate). You should still get spell enhancements nonetheless, particularly Cold enhancements as you get damage-over-time Cold spells, and it should help on your Winter Wolf-specific spells.
gives a good set of pointers for building one, from where I draw a few of the recommendations. Many people start with the Wolf form, then build for casting so that at endgame they get solid damage from their spells.
Take advantage of the Druid's proficiency with Scimitars and Shields, particularly if you're aiming for Nature's Warrior. Shield Mastery grants a chance to doublestrike, which applies to your natural attacks. Scimitars, on the other hand, deal a decent amount of damage, are slashing weapons (something the Cleric lacks if it attempts to go battle cleric) and have a high critical threat range, which means you can deal very decent damage even if not transformed (which is likewise good if the Druid is forced into melee and switch your spell-improving staff/club/scepter).