Control groups (CG):
CG 1 = First Meepo
CG 2 = All other Meepos
CG 3 = Third Meepo
CG 4 = Fourth Meepo
CG 5 = Aghs Meepo

You must also have "Unified Unit Orders" enabled on Options > Game > General. This will allow you control all your Meepo's all at once without wasting a control group for it. Just hold down "Ctrl" and move / attack and all your Meepo's will follow that order. It's respectively having a temporary control group (with all Meepo's bound) for as long as you're holding the "Ctrl" key on your keyboard. If you play around in a private game with this option, you'll get the hang of it really easily.

Blink Combo:
CG 2, Poof, tab, poof, tab, poof, tab, poof, tab, CG 1, Blink in to fight.
This charges 4 Meepos to poof on your first Meepo, they will then arrive to your target destination where your first Meepo blinks to. I also have my W bound to quickcast rather than normal cast, this lets me Combo faster without having to constantly click.

Farm as much as your team will let you in jungle / other lanes. You must make sure you're constantly checking your other Meepo's to make sure they're not getting ganked. Double tap the control group of a Meepo and it will switch the Camera to that Meepo. You must also constantly check the Mini-map as if you're checking your Car Mirror (every 3 seconds!). The less map awareness you have, the more vulnerable you are to ganks on alt meepo's, so you need to ALWAYS be aware!

If you have more questions or want more help on playing Meepo, then you can add me and hopefully I can help out.