Stereotypes are a good suggestion. "Lecturing" about them Office "Cultural Diversity Training" style is good. Cantrips and other types of pranks are good.
I suggest giving nicknames to other characters in the party based on their less than stellar performances in the past. "Trapfinder" to the character who has tripped "found" a trap or a monster. "Slick" for someone who has fallen in the party's own created Grease. Make sure to refer to them by those nicknames in public, especially to city official types. Or romantic interests.
Gather some pain-numbing roots and offer them to any female members of the party should they be skeptical of something with some comment about "that time of the moon, right?" Re-explain everything, especially very simple/obvious things, to the less smart, melee types of the party in slow, loud versions. "Remember, don't try to slash or stab those skeletons, they don't have skin!" (while you pull some skin out from your neck to demonstrate)
Applaud and cheer a weak hit for someone who just missed 5 swings in a row prior. "You keep forgetting to keep that shield arm up." to the one who keeps getting hit. "Let me count those coins, more than 10 here, and you are wearing shoes..." Have a very low strength score and lots of gear on a pack animal, that can't possibly be taken where the party needs to go - leaving your other members to carry your stuff.
Overall, be as helpful with your high intelligence as you can be. You can't help it that all your other party members are not smart and need your helpful suggestions All. The. Time.
Keep editing your posts well after other posts have been made after them. To include more jokes and jibes. And retroactively come up with even better ideas.
Talk to all 5 of the key party NPCs before anyone else in the party can post at all.
Laugh at the "jokes" others tell, showing how competent you think they are. Such as - "I'll take th e first watch and make sure we don't get attacked by surprise" - you respond with "Ha ha - good one. Just like you kept such a great watch last night... I'll set an Alarm spell 'just in case'." Blame your failures on others. Work in the phrase "I knew he was bluffing."
Space after each sentence as above, so that you take up near a half page with each post. (Having a long, poetry style spaced signature makes this even more easily accomplished.)
*Out of Character sincere, specific compliments where they are warranted can help keep the annoyance to your character and not you.*