1 day matches are all about getting in as fast as possible and these are a few things ive found that help:
1) On a batsmans wicket with plenty of sun pick your most attacking batting bowlers so that if you lose too many wickets then you can still add a few runs at the end.
2) Set your line up like this:
1-Neither aggressive or defensive opening batsmen, eg Jefferson
2-Aggressive batsmen but not your best.
Start both on normal until 1 settled bar is filled then set #2 to aggressive until 3 bars are filled then go to the first v. aggressive. With luck/poor bowling he should make 30-100 but his main aim is to get runs while #1 gets himself in. When #1 is on 4 bars settled move him to aggressive until you get to a point where you need runs, then go to v aggressive.
3-Good batter, not neccessarily aggressive
Bring this guy in if your #1 is out cheap.
4-Excellent aggressive batter
Bring him in when #2 is out or if your opening pair have lasted 20 overs+ and #1 is out. Put him on normal until he hits his first four then i just go straight to v aggressive.
5, 6, 7, 8 All rounders/keepers/aggressive batters
If there are more than 20 overs left when these guys come in then take it slow, otherwise v aggressive almost immediately.
9,10,11 Bowlers
You better hope there are 5 overs or less when these guys are in, just slog.
3) Bowl on 2 bars practically all of the time, less if someone is going well, 3 bars if you need a tailenders wicket quick. If someone does get it vary your length and line, not just to that persons weakness