Just what all does it take to win a bid protest?  Generally, two things:  1) a winning argument based on solid facts; and 2) an outside consultant to ferret out those facts.

Specifically, what kind of arguments win protests?  Let's get rid of the losing arguments first.  If you are dead set on arguing the source selection official's best value determination was a bad judgment call, you lose.  If you absolutely must argue bias and prejudice, you lose.  In these instances, I will not help you. 

So let me list the winning arguments:

1. The solitication language is ambiguous and must be clarified (pre bid protest).
2. The source selection official's justification is not thoroughly thought out and justified in writing (post award protest).
3. The source selection official failed to use all the announced evaluation factors, changed them or applied them unequally between you and the winner (post award protest).
4. The source selection official used an evaluation factor not announced in the solicitation (post award protest).

The first argument depends upon a thorough analysis of the solicitation documents including, in particular, the statement of work and the evaluation factors.  If they are ambiguous, go to the contracting officer pronto.  If he or she stonewalls you, protest.

The other arguments depend on what actually shows up in the agency record.  How do you see the complete agency record?  You must hire an outside consultant.  You will not be allowed to see the record, but your consultant can.  (I can explain.)

How do you protest without seeing the record?  How could you lose without the source selection official failing to apply an evaluation factor, changing the factors, introducing a new one or applying them unequally?