Don't worry about it right now. There will come a time when you will need to learn more in order to write the story well, but the biggest issue is WRITE IT. Everybody I network with on writing eventually learns and agrees that if you spend too much time on editing in the beginning or on making everything perfect, you'll never get the story finished.
WRITE FIRST. Even if it comes out crappy. The important thing is to finish off the story. AFTER the story is finished, go back over it and start editing. That's the time to learn the craft and improve your skills. If you start editing too early, you'll be editing forever and never finishing the story because you'll get into "perfectionist" mode.
So here's the order of operations for you...
1. Write the thing, even if your writing skills suck right now. Get it down; get it finished.
2. Learn something new about the craft of writing. There are tons of resources on the web. Take what you learn and edit your finished story to improve it.
3. Repeat step 2 until you're pretty sure you've got something good.
4. Join a PASSWORD PROTECTED writer's workshop. There are several out there. Submit a sample to be critiqued by others. Critique stuff that other people submit, also. Additionally, read critiques that others give to others. This is an important step, because
a) You need to be critiqued/evaluated by strangers. You can't trust the people close to you (friends and family) to evaluate you honestly because they have an emotional investment in their relationship with you. When strangers critique you, you'll get honest opinions and discover the weaknesses that you still need to polish up in order to make the story as good as you can make it. Don't take offense at any negative comments people give; the goal is to learn about the mistakes that you can't find on your own so that your book will be better and more acceptable to a prospective agent and/or publisher.
b) When you give critiques to other people in a workshop, it's more than just "holding up your end of the bargain". You actually learn by helping others the same way that others are helping you. This kinda reminds me of some saying I heard once about how you can learn something well if you study it, learn it twice as well if you question it, but learn it three times as well if you teach it. When you critique somebody else, you are taking the knowledge (even if it's only a little and incomplete) that you've gained and the insight that you've acquired and you're passing it along; essentially "teaching" it. This helps to reinforce what you've learned. Also, if you see mistakes that other people make in their writing, you can learn to more easily identify and correct these things in your own writing.
c) When you read critiques given by others to others, you are completing the full cycle of a writer's workshop. You learn by seeing mistakes that other people point out in stuff that you didn't write. Sometimes this makes it easier to learn about your weaknesses because you have less of an emotional interest in something you didn't write. You can then take advice that was given to somebody else and use it to make your own writing stronger.
5. Once you have polished up your writing skills and edited your book, you have to do some entirely different, yet related, type of learning/homework. YOU NEED TO LEARN THE BUSINESS END OF THE WRITING INDUSTRY. This is an important step that many writer's fail to do and they get ripped off or taken advantage of because they fail to do this. You don't need to be an expert on the industry, but you will need to learn a few things about how agents and publishers work together and how they work with the writer. You'll need to understand that there are more bad agents and bad publishers out there than good ones. You'll need to learn how to identify and avoid the bad ones and indentify and market yourself properly to the good ones. You can get some good resources on this by checking out the links at http://www.sfwa.org and reading the info at http://anotherealm.com/prededitors . Another good resource if you are trying to find out what agents are GOOD agents is to check out the Locus sales spreadsheets compiled by Melinda Goodin. This will basically show you what agents have actually made sales to publishers (that way you know the agents are legitimate and actually making things happen because they have the proper connections). You can access Melinda Goodin's spreadsheets at http://www.members.optusnet.com.au/~mgoodin68/locus.htm . Melinda does this work for free and allows anybody to check it out, but you should remember a few things that she notes on her website...
a) She would like for you to sign her guestbook so she can get an idea of how many people are being helped by her work.
b) She would prefer that you don't copy and paste the spreadsheets onto other websites. If you want to share the spreadsheets with other people, just post a link to her website instead, like I did right here. That way, she can look at how many hits her website is getting and get a good idea of how useful the spreadsheets are to people. Her work is a fantastic resource for writers; especially for ones who are just starting out and who are very confused. The more hits her website gets and the more entries she gets in her guestbook, then the more likely she is to continue offering this wonderful free service to people like you and me.
6. Take all the skills and knowledge you have acquired, make sure your book is the best it can be, and start searching for an agent!
Best of luck to you,
~Jamie Stromberg
http://www.myspace.com/Qmaus
EDIT: Address man...I DO agree with you that spelling, grammar, and rhetoric are all incredibly important skills for an aspiring writer to master. The reason I gave you a thumbs down is because I feel that your advice to do so, WHILE IMPORTANT, is premature. I network with a number of writers who are both starting out and already established and even though many of us groan, roll our eyes, and twitch in our seats when we come across poor spelling and overly-descriptive, nauseating passages, the consensus is pretty much unanimous: WRITE FIRST, EDIT LATER. Failure to pay attention to that key aspect carries a heavy risk of over-editing to the point that the story never gets finished in the first place.
EDIT #2: Laurem, you can't always trust spell check to be correct; it has a number of flaws. Also, the grammar check, even when it is "technically correct", will sometimes screw you over; you can't completely trust that either, especially if you're writing non-fiction, where the rules change to a degree. Eventually, you will have to learn and polish these skills.