Pre approval or deal first?

[Xia Ji]

Greetings! I'm interested in doing my first fix and flip and have been looking at hard money loans and portfolio loans. I've been doing some reading on the forums and I'm a bit confused about whether I should be getting a pre approval letter or find a deal first. Some say to get pre approved, others say the pre approval needs to be for a specific property or it is useless, and others are saying you need to have a deal to present to the lender for HML and Portfolio.

The market I'm looking to purchase in (Los Angeles) I hear properties are getting many bids and many buyers are making offers on multiple properties. I do have specific properties I am interested in, but they may not pan out if my bids are too low. 

What is the best way to go about this?