My issue is grammar and punctuation, also kind of getting carried away and ending up with way too much plot. My other one is frequent deletings and restartings. (planning just hasn't worked, so far my only two attempts were a disaster)
Dialogue I find fairly easy, but I don't put a huge amount of thought into it, I keep it simple and focus more on the actual interaction, and what is going on than the words spoken by the characters. I love banter it is so much fun or a major row - those scenes almost write themselves.
This I find is a really useful resource for the 'staging' of dialogue.
Bookshelf Muse
'casting' my characters with a real person is useful. I tend to use actors/singers that I can stalk round youtube. That way I know instinctively what their physical movement will be and it also gives them tricks of speech. I didn't do it with my first main character, but have with subsequent ones and it has improved my dialogue.
Description again comes fairly easy, but my university study was archaeology and I worked in a museum. Both of them involve describing an unfamiliar world to people. Again for me it is about keeping it simple and including just enough to create the image. Readers generally know what a wheel looks like and unless it is triangular they don't need to be told the shape
. The colours of the sea people generally know - so just need to say if it is blue, green or kind of dingy grey and how rough it is. Maybe describe how the light is affecting the scene to give feeling of time of day etc. In 2012 most readers have a greater world knowledge, so whilst in the 1890s I may have felt a need to describe the Eiffel Tower in detail, these days just saying the Eiffel Tower will give the reader the required image. I suspect that is why these days we don't need as much description, and most books contain more action. Also your character interacts with the setting, that is something I have got better with is building the setting, story and character together. An important thing ladies that write erotic fiction taught me was that my character has five senses with which to experience life with and not just sight or hearing.
I keep scrapbooks like this one for
Fresh Cream (my detectives) which i am currently keeping on my very defunct blog because of the handy applications. This helps with descriptions. For my not quite high-fantasy I have to use my rather rubbish art skills (stick figures lol) to make up the images that aren't available.