Credit Goes to Kitteh ^_^
1. Explain why you are there. One of the most irritating things is a person being at a place for the behalf of just being there, having no real reason on why they're there. So make up a reason for why you're are there even if it is a bit absurd.
2. Grammar/Spelling. Okay this should be a given but just for those people who butcher the English language, USE PROPER SPELLING AND PUNCTIATION!!! It doesn't have to perfect but when something can't even be read by others theres a problem. So try to use proper grammar.
3. Thoughts on the current location you're in. Describe your character's opinion of the location he/she is in. If it's hot describe how your character is feeling about the heat, does he/she like it, hate it?
4. Describe background. This is so everyone can have a sense for the area, allowing you and others to touch back on to keep consistency. Remember these descriptions shouldn't be plain like the sun is in the sky and theres grass. Make an effort when describing the terrain.
5. Describe Appearence. Describe what your character is wearing or not wearing O.o this allows others to look back at your description and describe you as good as your description was. This helps people improve their posts and more people will want to RP with you. You know they say a picture is worth a thousand words so be as detailed to create that picture of your character.
6. Interract with enviroment/do something. This doesn't mean you have to talk or anything unless theres an NPC or your replying to someone but you are able to walk, jump, crawl etc. Usually theres no problem in this aspect but when doing something put some detail in it. Use a thesaurus and dictionary it shows intelligence and we like that.
7. Describe the time and weather. Is it daytime or nightime? Cold or hot? Is the sky clear or really cloudy? All these things should be kept in mind and should be put into your post. It gives the setting more life and it's more enjoyable, it's annoying not knowing what the weather is.