All the bases are covered, so the paladin should do what comes naturally--be a secondary tank and healer. Since the Paladin has Lay on Hands, good hit points, good save, heavy armor, but few feats, he is a durable combatant but lacks the feats required to get the most out of TWF or even two-handed fighting. So tell your buddy to embrace the paladin's strengths and build as heavy a tank as he can. Optimally, the other players will never have to worry about coming to his rescue. He'll be a dependable rock.
Paladins get Turn Undead so you might suggest taking advantage of that ability via Divine feats. Divine Might and Divine Vigor are terrific.
Depending on the rogue's skill choice, it might be up to the Paladin to be the party face. So dump skill ranks in Diplomacy. For the other skill, choose something that fills a gap. Know: Religion is a good default.
Unless the player is planning on focusing on mounted combat, don't worry too much about Ride. Just summon the horse as a size Large independent speedbump or overland vehicle, neither of which require ride checks.
So, assuming 28 point buy:
Str 14
Dex 12 or 10
Con 14
Int 10 or 8
Wis 12
Cha 14 or 16
Int and Dex are the Paladin's dump stats, in that order.
Recommended feats:
1 Shield Specialization (human bonus: WF: long sword)
3 Power Attack
6 Divine Might
9 Divine Vigor
Heavy armor (mithral full plate if you can get it), large shield, cold iron longsword, adamantine morningstar, silver battle axe, a couple light hammers or javelins, dagger, composite longbow (+2 str), mix of arrow types, oil, holy water, lantern, sunrods, holy symbol, rope, spikes, backpack.