Welcome to Gaia! ::

Less, is not always more.
If you run out of things to say, describe things. RP isnt just about a conversation. Its everything that goes hand in hand with that conversation.
The surrounding, the other person, what has happened, what could happen, what your character is feeling.

So instead of your post being;
Gary looked at Celia. "Yes, I love you." He blinked and smiled.
Why not stretch it. Give your RP partner something to reply to.
Try this;
Gary smiled at Celia, light dancing in his eyes. His heart was racing, it felt as if it was punching his rib cage, to try and burst through his chest.
"Yes, I love you."
Gary's throat felt dry. He rubbed hsi neck. The light pouring through the window was resting upon his dark jeans leg.

Notice the descriptive sentences? I didnt write a novel, but there is ample to respond to.

When less really is more
I know the last tip was about having more. But that does not mean write a novel. No one wants to read about every little description. We dont care about the reflection off every lens of the fly on the walls eyes.
Also, dont spend 5 paragraphs of just actions for your character. The rest of us would like to jump in some time. It's a group roleplay. If you want to write a novel, hit your word processor.

Consideration is always appreciated
Think about everyone in the RP. Not everyone wants extreme cursing.
If you have authorisation to use an NPC, we dont want a vampire who is going to turn everyone in the villiage.
Use some literacy. Try "Hi, how are you?" as opposed to "hi how r u?". Trust me, the way to a writers heart, is his eyes and the crap he doesnt have to read.
And most importantly, post appropriately. Make some sense for crying out loud.

Think one step ahead
And no, I do not mean 'Which is the best way to outsmart the enemy'.
Think ahead of your post. Where do YOU want this RP to head? Think of your goals, wants and needs. Other people are either a help or a hinderance. Sometimes, if you are good with your words, you will be able to get your partner to appeal to your bent, without them really knowing. Or maybe they do know it. Are they lulling you into a false sense of security? Probably not. Maybe they think that you have an idea worth pursuing.
A good RP is like a relationship. Good communication helps. Its not like talking to Lassie and deciphering a bark. Oh right, the barns on fire. Never gonna happen guys. Not now, not ever.
If you want to plan your RP ahead, we have an OOC subforum, and you can PM your parner. Whether they answer is up to them really.

NEVER GO ANYWHERE WITH A BLINDFOLD ON. This applies to RP also.

OOC and IC
When you are In Chracter, you usually type in third person.
{ Jamie walked down the road. "It's sunny today," He said gleefully. }
Sometimes, you can use first person.
{ I walked down the road. "It's sunny today," I had said gleefully.
These are examples of past tense.
You can use present tense, but it gets confusing in RP.
{ Jamie is walking down the road. "It's sunny today," He is speaking gleefully. }
And in first person.
{ I am walking down the road. "It's sunny today," I was speaking in a gleeful tone. }

I practically beg of you, use the green one. It is easiest to keep track of, not only for you, but everyone else also.

When you wish to speak Out of Context, make it obvious.

Jamie walked down the road. "Hello," He said to the people he met.

[Do you think maybe we should hang out next week?]

In this example it is clear to see where the OOC text is. Make your IC and OOC seperate. Dont confuse yourself. If you are confused with yourself and your posts, how do you think we feel.