The rules of how the guild upvotes are here. I encourage all promoters to read this. Basically it's now the job of the Steem Ambassadors (currently 32 of them) to curate on the #promo-steem posts. If there is a concensus reached on a particular post then they will receive an equal share of an upvote from@steem-ambassador in the next upvoting round (1 round per day). Once this is done, it will trigger an upvote from the @steem-ambassador AutoTrail, which will add further upvotes to the post.

This filters out spammy/plagiarised posts, and makes sure that the voting mechanism is completely decentralised.

So if you want to get upvotes from @steem-ambassador, it's important to make sure your posts meet the community guidelines.