This achievement can seem really hard to get. The clips are reset on midnight GMT of 25th of every month. If you want to get the achievement you should try and do it around this time. Here is what you need to do:
1. First check how many downloads you need to get into the top 20. If it is just after midnight (GMT) on the 25th it should be less than 50.
2. Create a short clip so that it is quick to download. Share it.
3. You need a second gamertag. Create a new silver account or just create a free trial Gold membership.
4. Add yourself as a friend to the second gamertag.
5. Go to 'Friend's Clips' on the secondary gamertag and download your clip.
6. When the clip is finished downloading but before it starts playing press your XBOX Guide button and sign out. You will be thrown back to the Burnout start screen.
7. Sign in again with the secondary profile and repeat from step 5.
8. When you have enough downloads sign in with your primary profile.
9. IMPORTANT! You now need to go to the "Top 20 Clips". If your clip is on there you will get the "Celebrity Status" achievement!
10. Now unshare your clip to make it easier for everyone else to get the achievement as well! Good luck!