Some of the best advice I can give you,
React. Don't dodge for no reason. Dodge, and know why you are dodging. Anticipating your opponents moves is good but if you dodge too soon, he can anticipate where you will land and meet you with a rocket or a shock combo.
There are times where you have to dodge out of the way. Try to plan ahead so you can draw your sheild gun the moment you become vulnerable.
Also, don't bunny hop or jump for no reason. This is the single biggest mistake I see new players make. I know with double jump you seem to be evasive and hard to hit. The exact opposite is true. When you are in the air, your movements are predictable. You have to land correct? Your opponent will visualize your landing spot and meet you with bullets.
All this does is to help with what someone else has already said, be unpredictable. Strafe left and right quickly to throw your opponent off. Never run in a straight line.
A few last things
- Single dodge > double dodge in most cases (again, quicker therefore less anticipation allowed by the enemy)
- Don't be afraid to double dodge forward with flak or mini drawn to surprize and get in close for the kill. It takes some work to master but this is very effective if the enemy has an LG or SR drawn.
- Don't be afraid to run away and use cover to take some pop shots as you retreat to find more health. Charging relentlessly at your opponent again makes you predictable.