After conducting an extensive search online, I couldn't find a satisfactory answer to the question of how to create bookmarks within a SharePoint 2010 wiki page. This led to some experimentation, and I concluded that the simplest way is to use the Insert Link feature in SPS 2010.
In order to demonstrate this, I will create several paragraphs with headings, assign bookmarks to the headings, and then link to the bookmarks.
You could start with a simple wiki template and add a table where you would list a wiki style bulleted table of contents, or you could opt for a template with the summary links web part. I have chosen the Summary Links (Article) page layout for this article.

Create Body Text

 Fill out the page content area either by typing your text, or pasting it from another source. Separate your body text into paragraphs. In this example, I will add headings and styles to the paragraphs.

Create Headings

Once you have entered your body text and added the headings, format the headings to make them stand out, as follows:

  1. On the ribbon, select Format Text, if not yet selected
  2. Highlight the heading text
  3. Click on the Markup Styles button on the ribbon
  4. Select the desired heading style

Create Bookmarks

Now that you have the text and the headings in place, you can create your bookmarks. Bookmarks can be created in any location on the page, however, for clarity, I will create them on the paragraph headings.

  1. Highlight the paragraph heading as you did above
  2. Click on the Insert button on the ribbon
  3. Click the Link button on the ribbon
  4. This will open the site assets dialog box. In the left pane, navigate to your page library and in the right pane, select the same page that you are working on, then click OK
  5. On the ribbon, under Link Tools, type a bookmark name in the Bookmark text box, such as P1, or bk_1, or anything that makes sense to you
    When you click on a different area of the page, the changes you've just made will be saved

Create "Table of Contents" Links

  As I mentioned earlier, you could use a regular table and populate it with links. In this example, I will use the Summary Links web part included in the page layout in the top-right corner.

  1. On the Summary Links web part, create a heading if necessary, by clicking on New Group
  2. To create the bookmark link, click on New Link
  3. In the Links dialog box, select the page you are currently working on
  4. BEFORE clicking OK, notice the selected web address in the Location (URL) text box at the bottom
    1. At the end of the web address, type the # sign followed by the bookmark name that you created as seen below, such as bk_1
  5. Click OK

You can repeat the steps to create multiple bookmarks, including a Back to Top [of page].