Keyword Density
It is usually suggested to find 1 3 keywords for your content, but extensive research is required to find out which keyword is most searched for, after all its no point of optimizing your website for the keywords that no-one is searching for. So make sure you do your paperwork and jot down which keywords are most searched for and with less competition. Write as many keywords you think of, dont just limit them. You should be able to build up several phrases from them. While thinking of any keyword search think about following

1. List down the purpose of your website. You will definitely find some words here.

2. What would you type in the search engine if you want to find out your website?

You can use Overture for your keyword research. This tool not only shows you how many searches have been made for a given keyword in past month but all shows you several alternatives for that keyword. The other keyword research tool I can suggest of is WORDTRACKER. Although they require subscription, but OVERTURE is completely free. Search engines like Google also provides with good recommendation tool although it does not indicate any popularity.

Measuring Competition for Keywords
After you are done with your keyword research for search engine optimization and short listed all phrases its now time to find out the competition involved with them. The best way to analyze competition is go to any search engine and type your keyword. This will show you number of results return.

In order to make this task easier use paper-based or excel worksheet as done below:

Keyword Term: keyword research article
Date of Search: __________
Top ranked site: _____________
Search result: 46,900,000
No of searches made in OVERTURE: X numbers

Likewise repeat the same procedure for your other phrases. This will help you to do various comparisons between several key terms and select the best niche keyword.

Applying Keywords to your content
Make sure to keep 3-4% of keyword density. Use your keywords as following in the body of your webpage content:

• Title Tag: Title tag content is displayed on your browsers title. You can use about 70 80 characters here. Make sure to use good combination of you keywords here separated by |. For example for our keyword research articles keyword we can use Keyword Research Articles | Keyword Analysis | Keyword Optimization.
• Meta Description Tag: Write meta tag description of about 200-250 words include you most relevant keywords.
• Header Tags:> Always use your main keyword in h1 tag and combination of your keywords in h2 tag. h1 can be used as headings and h2 can be used as sub-headings.
• Body Tag: This is where you spread you keywords. Make sure you have at least 300 words in your body content where you use you keywords in the first 25 and last 25 words of the body tag.
• Img Alt Tag: If you are using images always provide alt attribute which shows your keywords.
• Anchor Tag: Text appearing for any link is called anchor tag. This has high relevance in any search engine.
• Webpage name: Having keyword name as part of you webpage name is also very important.

Summary
So keyword research is the heart of any Search Engine Optimization task. Without any firm research you will not be able to rank high and ultimately your onpage SEO suffers. Good niche keywords turns into traffic which converts into sales conversion.