What is best pass depends on many factors, what works best for you, size and skill level of your opponent, etc. In other words multiple people will have multiple answer based on their personal styles.

Still there are some basic principals that you want to follow when opening guard that are universal and work well.

Step 1. Make sure you are safe

You want to ensure that your opponent stays away and he is locked against the floor. That will prevent him to sweep you, get your neck in guillotine, control your arms (which leads to arm bar) or set up triangles along many other options. People do that with grabbing on belt and pushing it up or on gi. You use that to push yourself away against his chest. In no gi fight you can push on his hips and stomach (same idea).

Few tips to be remember,

1. keep your elbows in - close to your body, if you don't he will pull them outside and break your posture

2. keep your balance as you start breaking those legs, the moment they break open many guys try to convert to scissors sweep and its variations.

3. if he is trying to get choke (hands are going up the collar of the gi) push him down away from your self and extend his arms - that will set your neck free and get his fingers tired fast. (there is few more tricks - some other time)

Step 2. Break the lock

Once you are safe and away from danger (it seems like you get there with no problem based on what you said), you need to create unbearable pressure on his legs (ankle) lock, and force him to let it go. There are 2 main ways to do this and many variations. One is to create good save posture (some people stand up and then using your free arm push on his knee until lock breaks, other is to use both hands on body, move back-worth with body and manipulate body to crash open those leg locks. Both work, try them and see which one works better for you. I will include some youtube videos that are real deal, so you can experiment with it, and find what works best for you:

Saulo Ribeiro

Mario Sperry

Have fun, let me know how it worked for you.