Optimal police investigation strategy

I admit it - I watch too many cop shows on TV: Law and Order, CSI, Cold Case, etc. In all these shows, the police go with their hunch, browbeat a suspect until he/she confesses or gives another lead (or in the case of CSI, the evidence might point another way) and then chase the new lead to another suspect and brow beat them again until they catch the killer. I've often wondered:
1. Is this really how police do their work?
2. And if so, is this optimal?
3. Are police hunches really/experience useful or should they just follow the evidence (a la CSI)?

On a 40-minute show, yes it does appear to be the optimal strategy. Browbeating a suspect does yield useful leads but what about in real life?

The Washington Post is currently running a series on the murder of Chandra Levy. Their main thrust so far seems to be that the police went on a hunch that she was going to meet some one (probably Gary Condit) and excluded all other possibilities until it was too late. Too late in the sense that by the time they could exclude him they were already unable to follow whatever evidence they had. By the time her body was discovered all the evidence was compromised. I believe that they had hope that Condit would confess and tell them where the body was which may have been why they did not do as thorough a search as they might have.

So far, I've concluded the following:
1. Yes, they really do follow their hunches/instinct/gut what have you.
2. Yes, they really work like they do on TV (or maybe it should be the other way around).
3. In real life it isn't optimal - life is not a 40 minute cop show and yes they really need to gather the evidence and follow it despite what their hunches tell them.
4. This is not to say that they should not also purse their hunches because I believe that experience is important.
5. They need to guard against a herd mentality so having a nay sayer or someone who is willing to go against conventional wisdom at the time is important. (Remember the white box truck during the sniper shootings that turned out to be a Chevy Caprice?)