If you want to force your Android phone to check for updates (ROM updates, not App updates which updates through Market), here is a little trick for you:

First, you could try checking for updates from the **Settings menu -> About -> Updates
**(May vary depending on your model).

If that did not work, you could try this trick:

Open your phones dialer, type ##2432546##**

(Or  ##checkin## if you like). Just as if you were going to call a number.

Your phone should now check for updates to your ROM.

Note: This does not work on every model though.

Please post in the comments if you succeed!