bidding strategy

Hi all,

I am wondering on the approach on the strategy of bidding and monitoring from there.

Take for example, say after keyword research we come up with 200 keywords (compare and buying keyword), we break them into adgroup.

(I am talking about at the initial launch stage)
1) Do you set all the bid price the same for example all at $0.50, or set different keywords at different price?

2) Does anyone take a "Top - down" approach, that is to say, set a high bid price and monitor what keywords convert and from there adjust the bid price downward such that there is a better ROI. Or a "Bottom-up" approach, start the bid price low, slowing adjust upwards.

For me, I tend to do a "top - down" approach, I bid at high price (prepare to lost some money) so that I can have enough traffic statistic to see what are the potential converting keywords and from there adjust the individual bid price downward to find the breakeven point.

Anyone care to comment or share the bidding strategy?

cheers
roy