Need tips for auction

[Jennifer Jones]

Im a newbie and recently registered for a tax lien auction  for blighted properties and county tax recovery. I noticed that some of the same initials are repeatedly on the registration list. Do i assume these are investors, whats my stratetgy... go against them/stay away? What % of the assessed value should i go up to?(auction starts at $400) i have 18 properties im looking at, shld i focus on out of state tax holders vs in state? Pics are avail and county lists property as poor, avg, or fair...what tips and strategies...looking to rehab and rent after the year wait. Thanks for any input.