I've been doing this for years. Here are a few quick tips on what I do. It's somewhat ruthless, but then the proportion of scammers, chancers and clueless crooks in Flippa requires ruthless. You may miss one or two good sites, but I prefer that to losing huge amounts of time by not employing these rules.
1. Browse the homepage listings and exclude any site that says $xxx in last 30 days (or some variation of that). Grounds: Too short term. It hasn't proven itself as a sustainable business. Only four out of 30 sites on the frontpage today are more than a few months old! Use age as one of your filters when running filtered searches.
2. Also exclude any site that claims Google first page spots in the title. If a fleeting spot in the SERPs for some obscure term is their claim to fame, that ranking may disappear even before the end of the auction!
3. Obviously sites that are clearly not in my area of interest - gaming sites, celeb sites and other sites in niches where a lot of activity is accompanied by relatively low levels of income aren't sites I specialise in. Also high risk BS such as autogen sites.
4. Titles that suggest a lot of custom coding on the site. I can't be bothered hiring people to sort out someone else's bugs
5. Ignore the titles and run your eye down the "Est" sections. Anything established relatively recently is avoided.
6. Do the same with PR and Profits and Visitors (unless you've used Flippa's filter to fine tune the search)
7. Ignore any title that suggests the listing could be full of hype. The seller is looking for a fool who'll value the site based on the seller's opinion rather than the business facts.
8. Ignore any title that suggests it was written by a career "siteflipper" (they are formulaic and go by all the advice in siteflipping ebooks e.g. "$1 reserve")
9. Sites that mention potential in the title. It's going to be overpriced
10. All caps. Too juvenile. It's unlikely to be a seller I can work with.
What turns you off in listing titles? Are you going to share?