Keywords
Keywords is what gets you organic traffic. If the google spider believes that you belong high in certain keywords than the traffic will go up as your site will be listed higher. Of course this depends on how competitive the keyword is and how many searches that term gets from people on the internet.
Putting in the correct keywords
You have a website about dogs. You shouldn't have the keyword "Muscle cars". People are going to search that term and they will get your dog site? that's dumb. Actually to be honest you won't get a single person because google will crawl your site and find all of these puppy stuff and won't list you in “muscle cars”.
Be smart about it. Your keywords should be something like “Dog lovers, K-9s, puppy info” etc. Some people use only a few keywords, and others use like 20 of them. I'm not exactly sure what's better at this point myself. If you have too many than you will not be able to optimize the keywords.
Choosing the right keywords
Now it's more tricky than that because some keywords are typed in google like 40,000 times a day. For example "Dogs". if you have “dogs” as one of the keywords don't expect to be first on googles list when people search it. After all, there's only probably 10,000 sites that are more SEO-ED than your site that are using that same keyword. Even something like "Big Dogs" would be hard to rank well. If your site is new than you better use keywords that are not in so high demand. Hmm, how about "family dogs information"? I don't have statistics in front of me but I'm assuming that this gets about 300 searches a day. This is the keyword you need to be running with. Pick a few more keywords now then your done for now. Too many keywords and you won't be able to control them to bring them up in the ranks.
Spelling errors and keywords
Some people use common typing errors for keywords because many people accidentally type this in google. This is hard though because you have to find a word that is most easily typed wrong and yet again competitors already have that keyword. If you go to google and search "keyword Research" it will strongly help you if you find a good site.
Keyword programs
If you search in google for keyword research sites make sure not to pay a dime to anyone for this information. There are a few highly respectable sites which pretty much all professionals use and they are very good.
https://adwords.google.com/select/KeywordToolExternal
This is googles official keyword research tool. It's commonly used for individuals using adsense in their site because it offers an estimation to keywords and their ad click worth. Fortinatly, this can still be of use to you as well because it still shows total estimated searches for keywords.
http://freekeywords.wordtracker.com/
My personal favorite. Wordtracker. It's simple, it's quick, and its somewhat accurate. You type in a keyword and it gives results with that and 50 others like the keyword that you are in common with what you typed.
http://www.seochat.com/seo-tools/keyword-difficulty/
This is not for keyword research. It is for checking how competitive the keyword is. You need to make sure that there isn't too many people using the keyword that you are thinking of using because it'll be near impossible to beat them if your just starting out.
http://inventory.overture.com/d/searchinventory/suggestion/
Overture keyword suggestion is evil. It's the number 1 used site for keyword research in the world, but I hate it. Once I spend over $3000 using a special keyword that I found. It had no competition, but a huge search ratio. I got the site built, bought out advertising before my cover was blown, but the stupid overture was a mistake. It wasn't correct. That keyword didn't have competition because it didn't have a single search from anyone in years. I spent all of that money and for what. NOTHING. Back to the point overture, I believe is a great tool for keywords. Everyone else seems to think so. It just so happens that I have a personal grudge against it.
