First, see Brian Abbot's documentation on the topic

It's worth emphasizing that you should mind the "Automatic alias" checkbox in the "URL Path Settings" section of the page. You want this unchecked if you have entered a custom alias before. If the existing alias is fine (e.g. if you like your site's automatic alias settings), then don't worry about it.

If you have been set up with the "Workflow Access" Drupal modules (and therefore see various workflow options available to you under a box labeled "Draft-Done"), then be aware that this works in conjunction with the "Publishing options" box at the bottom of the page. If you are using the advanced workflow, you still need to have "Published" selected under "Publishing options."

Finally, be aware that you have revisioning at your disposal. Under "Revision information" you can create new revisions after you've initially added the page to your site. This is handy if you have to undo anything in the future.