Lean towards radio or checkbox lists instead of select menus.
Wrap radio and checkbox inputs and their text in <label>s. No need for for attributes here—the wrapping automatically associates the two.
Form buttons should always include an explicit type. Use primary buttons for the type="submit" button and regular buttons for type="button".
The primary form button must come first in the DOM, especially for forms with multiple submit buttons. The visual order should be preserved with float: right; on each button.
Make use of <thead>, <tfoot>, <tbody>, and <th> tags (and scope attribute) when appropriate. (Note: <tfoot> goes above <tbody> for speed reasons. You want the browser to load the footer before a table full of data.)
<tablesummary="This is a chart of invoices for 2011.">