Wizard: I'll roll to Aid the Figther on his attack roll.
Fighter: Can you roll play that for me?
Wizard: Um...I pat you on the butt?
How would you roll play when you Aid Another with her skills?
PC: Psst! Be extra stealthy...
Wizard: I'll roll to Aid the fighter on his attack roll.
Fighter: Can you roll play that for me?
Wizard: "Orcus has a big butt, Orcus has a big butt! Neener neener!" Now he's looking at me. Hit him.
For Aiding stealth:
Beforehand
Wizard: "Ok, watch out for that dry twig there *points* and that leaf *points* and that sleeping cat's tail *points* and that rabid dog *points and has finger chewed off*..." I failed my Aid roll.
Attack Roll: "I throw a rock at the goblin to distract it for a moment."
Arcana/History/Religion/Nature: "I'll help you with your research give a topic to look up." or "I'll suggest some details he might not have considered and act as a sounding board; we'll discuss the situation".
Perception: "Look, over there - what is that?"
Diplomacy: "You should listen to what Hank says, we have traveled together for years and he has always always been a fair and honest friend - I would trust him with my life."
Intimidate: "I'll stand behind her while she is talking and scowl menacingly with my hand on my sword handle."
Athletics: "Don't step on that rock, it looks lose, use that one over their."
Stealth (assuming you are not trying to stealth yourself): "Hey you big stupid ogre, look over here!"
Bluff: "She couldn't of stolen the jewels from the temple, she was with me the whole night."
Stealth: Silently pointing to the loose floorboard. Or offering a hand to get over a noisy bunch of gravel.
Diplomacy: "Can I get either of you a drink? You must try this elvish caviar! I must say, that's a fine robe - Tommy Hillgiant, isn't it?" Or just paying rapt attention to the PC you're helping, nodding as if every word was pure gold.
Intimidate: (Whispered to NPC) "Don't make her angry. You won't like her when he's angry."
any Knowledge check: "Aw, c'mon! You were just talking about this the other day! You know, you were trying to lecture us again, and we weren't listenting as usual, but I remember it was about just this thing...it was an elvish thing - no, tiefling, right?"
Insight: "He might be lying - see, he's got that funny eye twitch, and on most folks that means he's lying. I dunno if that works with halflings, though..."
Perception: "Sh! Did you hear something?"
As far as skills go...well, last session, the warlord used Aid Another to help the rogue climb up out of a pit, literally by giving him a hand. Other times, it's less physical help and more verbal tip-giving.
-If he's aiding someone in combat, he waves his staff annoyingly in the enemy's face and generally makes an "old-man nuisance" of himself.
-During a skill check, his attempts at aiding others generally boil down to telling the other characters that they're doing it wrong, and that in his day he used to have to make diplomacy checks, 15 miles through the snow, uphill both ways.
(alternatively, he'll tell them that in HIS day they didn't have armour class, climing pitons, swords, etc)
FWIW I've renamed his spells such that his "Sleep" spell is now an "Onion", which he proceeds to explain that back in his time he used to wear this onion tied at his hip - since it was the fashion. He used to wander all the shadowlands looking for small beetles that would help in the diplomatic relations of the large pine trees in the north and the women's bath area that sometimes a few people would visit when he was hungry...
*enemy fails save next round*
Its really going to depend upon what action is being aided but here are a few possibilities:
Attack Roll: "I throw a rock at the goblin to distract it for a moment."
Arcana/History/Religion/Nature: "I'll help you with your research give a topic to look up." or "I'll suggest some details he might not have considered and act as a sounding board; we'll discuss the situation".
Perception: "Look, over there - what is that?"
Diplomacy: "You should listen to what Hank says, we have traveled together for years and he has always always been a fair and honest friend - I would trust him with my life."
Intimidate: "I'll stand behind her while she is talking and scowl menacingly with my hand on my sword handle."
Athletics: "Don't step on that rock, it looks lose, use that one over their."
Stealth (assuming you are not trying to stealth yourself): "Hey you big stupid ogre, look over here!"
Bluff: "She couldn't of stolen the jewels from the temple, she was with me the whole night."
This is sort of similar to what I would do. Although with a wizard I would put a bit more magic in.
Attack Roll: "Aaaand sudden bright flash of light in the eyes." "Turn foot asleep right about...now"
Arcana/History/Religion/Nature: "Take this book. And this one. And possibly this one. Here I marked the pages"
Perception: Same thing, not that this would ever see use.
Diplomacy: Again same.
Intimidate: "hmmm...bored" juggling fireballs, casual lightning discharge between the hands, "Can I shoot him now? Please?"
Athletics: "Don't step on that rock, it looks lose, use that one over their."
[b]Stealth (assuming you are not trying to stealth yourself):"Aaaand sudden bright lights in the face."
Bluff: "Look my divinations on the Jewels said nothing about a temple. A gem mine was mentioned, as was a cart, but no temple. These gems were never in a temple. They seem to be given around a lot though, four gifts, and they've been through five merchants.