I have been going over this site http://www.zencarttips.co.uk/?p=48 to help my optimize my current site. When talking about the h1 tag specifically. Is it best to tag the whole paragraph or just the bold keyword?
Do not make an entire paragraph into an <h1>. Google evaluates individual on-page elements like <title>, <h1>, <h2>, etc. the same way they evaluate the entire page: Things near the beginning of the HTML element are considered more important. Keyword density within the HTML is important. A properly optimized page will have undergone keyword analysis to determine a single keyword phrase (maybe 2 or 3 phrases if they are almost identical) that the page will target. Then you should optmize the title (most important on-page ranking factor) and optimize the meta description (meta description doesn't affect Google ranking but DOES affect click-thru-rate) for the targeted keyword phrase(s). The <h1> should reinforce the targeted keyword phrase(s) from the <title>. It's okay to use a few "fluff" words in the <h1> to make it "catchy" from a marketing perspective, but try to include keywords from the targeted phrase FIRST in the <h1> if possible (or near the beginning), and minimize the number of words in the <h1> so that you don't dilute the keyword density of the targeted keywords.
In my experience you should only have 1 x H1 tag on any given page of your site.... anymore than that and google will not be too happy, i have tested this many months ago... try and use your main keyword (as the header for example) Regarding H2 & H3 go with the rule of only use 2 x H2 tags and 3 x H3 Tags 4 x H4 Tags etc... It has worked for me. The only thing i would say is dont use the tags mid paragraph in you can help it. Good Luck