Once Header Tags is installed, follow these steps for a
basic setup:

1 - Go to admin->Header Tags SEO->Fill Tags, scroll to the
    bottom of the page, click on the Fill All Tags button
    for each section and click Update. Check the results
    on that page to make sure there are not any errors noted.

2 - Go to admin->Header Tags SEO->Page Control and fill in the
    Title, Description, keywords and Logo Text boxes in the 
    default section (right side). The text should be something 
    relevant to your site. Uncheck all of the check boxes in the
    Include section. Click Update.
    
3 - Go to admin->Header Tags SEO->Page Control and select index.php
    from the dropdown menu. Change the text in those boxes to something
    relevant to your shop, or clear them, and click Update and the bottom 
    of that section.
 
4 - Go to admin->Header Tags SEO->Test and click on the Test button. Handle
    whatever errors are displayed.

5 - Go to admin->Catalog, select a category and click edit. Enter in the 
    categories description for that category (large box at bottom). That 
    text will be displayed on your category pages and should be text related 
    to that category. Do the same for the other categories and the
    manufacturers is your shop uses them. These are important but can be
    done over time.
    
6 - Go to admin-Configuration->Header Tags SEO and change the settings to
    your preferences. I recommend that the Social Bookmarks, Tag Cloud and 
    Enable AutoFill - Listing Text options be set. The keyword highlighter 
    is also a good option to use but the results vary depending upon the 
    site so you need to test it to see if it works well for yours or not. 
    It will highlight the keywords on the page and some sites mention the 
    keywords many times, which is good, so this option ends up highlighting 
    a large number of them, which is not so good.

7 - Go to admin->Configuration and set the Search Engine Friendly option to 
    false, if it exists.

8 - If you want to use the model cross reference page, you will need to add a link
    to it somewhere. The information box is where such things usually go but it 
    can be anywhere you like. The link for the box will be something like this (use
    the other links present to compare against):

 '<a href="' . tep_href_link('model-cross-reference.php') . '">' . BOX_INFORMATION_MODULE_CROSS_REFERENCE . '</a><br>' .

9 - If you want to use the additional words option, for Bootstrap and some versions 
    of 2.3.4, go into the modules_>content_>Product Info section and install it. For
    other versions, the code needs to be added to the product_info.php file. See
    the included file for how to do that. Then turn on the additional words option
    in the settings.

10 - Go to admin->Modules->Header Tags and remove these modules:
    category title
    manufaturer title
    product title

I realize no one likes to read instructions but the buttons at the top of Page
Control will, hopefully, make that a little less painful. 

************************** IMPORTANT *********************************
If you post a problem in the support thread, be sure to mention the
version of oscommerce you are using. Otherwise, your post may not get 
answered or it will be delayed while you find that.
************************** IMPORTANT *********************************

http://forums.oscommerce.com/topic/298099-header-tags-seo

Free support questions will not be answered if you PM me or contact me 
through my web site so please do not do so. 
