I'll leave technical advice alone since I'm a right handed opener , but essentially don't change too much , just adjust your game as you learn what works for you ....and watch good players .
Preparation is very important for openers , you won't be sitting around waiting , you know when you are batting , so use that to your advantage. For me , I'm nervous , so like to get padded up early so I'm not in a rush . I hate throw downs , instead i visualize batting straight for a while . Then i like a laugh /chat to take my mind off things and I'm usually right to go . Don't second guess yourself on game day . The middle isn't the place to totally reevaluate your approach/technique.
Personally, I try to avoid any directional thinking . No 'how quick am i scoring' , 'i need to play this shot' , 'i want to be at x runs after x overs' , ' i need to be not out after x overs' . I just try to bat with the same feel as my net/bowling machine practice , where I'm just trying to play each ball as best i can . Then wipe my mind after the ball is bowled and do it again...'rinse and repeat' ! The runs will come .
Lastly , if you're playing limited overs cricket you cant leave balls forever , but leaving is still a good tactic in moderation as it makes bowlers change their lines to bowl more at you and then loose balls often follow ( which is probably handy for you if you tend to on drive and glance off your pads). Just remember that every ball you face early in the innings is one less opportunity the opposition has to use the new ball against a new incoming batsmen -and after all , your team mates in the middle order want to actually bat in the middle order ( they make their runs better against an older , lower bouncing , softer ball ), not at 4-6 after 4 overs .