For digital releases, please use 
exclusively!
For physical releases our addresses are:
The Metal Observer
c/o Larry Best
11 Warwick Road,
Milford Haven,
Pembrokeshire,
Wales
SA73 2LP
or
The Metal Observer
c/o Eric Ward
273 Countryhaven Rd.
Encinitas, CA 92024
USA
We CANNOT guarantee you a review of your release, no matter if label released or independent. We received hundreds of promos every single month and while we put all of them up for claim for our reviewers, it is impossible to be able to review everything (as much as we would love to). We do our best, though, to get as much reviewed as we can.
Other than that it is simple:
Make sure that the style fits into our spectrum (we are a METAL site).
Make sure you put the correct ID tags into the files.
Send us your stuff as a .rar or .zip (no streams) via an upload service (Mediafire, Yousendit, Dropbox, Bandcamp etc.).
Done. We’ll take care of the rest.