Big on-page changes: all at once or little by little?

[DoMiSoL]

Hello,

I have a website with bad urls (http://www.domain.com/site/page.php will become http://www.domain.com/page.php) and bad titles (keyword stuffing) and I have to fix all of them.

Should I change the urls (and, yes, make the proper 301 redirects) and get crawled by the S.E., before I give a unique title for each page  or viceversa?

Or maybe shoud I do everything at once?

What's the best practice to minimize the ranking drop and how long will it take to resume (and increase) the previous ranking?

[gmk1567]

I would recommend to update pages as soon as you complete each change. Since no one knows about the accurate Google process time for each change, no need to connect your changes.