Avoid the following -

1. Perrenial losers. Check win strike rates.
2. Horses that are way under the odds due to media beat ups. I'm sure plenty of owners get the irrits when they see $2 about their horse that should be $4. They wait for another day to pull the stick.
3. Horses that perform exceedingly well last start. By exceedingly well I mean beyond what they are normally capable of. They have often burnt themselves out and don't stand up next start. An example. Average welter horse is in the Epsom on the limit and runs a 3.5 length 10th and rates about 6 kgs higher than usual. Is now back in a welter as $2.0 fave. Runs 5th beaten 4 lengths and everyone wonders "how did he get within 3.5 of so and so in the Epsom?". Answer - raced beyond his capabilities and is now paying the price.