jungling mechanics question: neutral creep targeting

I'm going nuts trying to perfect my micro on jungling with e.g. Enigma, Furion, etc. Several hero builds for jungling require clarities in the first few minutes. Stoopid trolls and satyr mages kill that...

What are the mechanics that determine whether ranged neutral creeps attack the hero v.s. summons when your group is attacking a camp? E.g., eidolons have to get closer already for their 450 attack range, but those ranged creeps keep taking potshots at Enigma even behind them with his 500 range.

Can't find the answer w/ Google. Any help?

Generally, they will attack who ever was there first, so if you have pre-summoned units, wak them to the camp first, then go in. WIth enigma they should auto target to the eidolons when you eat a creep. Not sure why you might be having problems.

Hmmmm.... makes sense, but usually they attack the eidolons for about 2 shots, then shoot off my clatiry. Or esp. w/ the trolls (trolls...) even if I march the ediolons in ahead of me the auto-target Enig.

NP is less of a problem, but still sometimes if I'm focusing the trolls or satyrs on the left, then the right one will break off spontaneously and take a shot at the hero.

Are there any posted mechanichs re: the protocols for creep targeting? Anywhere?

If you have autoattack on you should turn it off.
Creeps always target the closest attacking target. Autoattack basically fires an attack command at everything in range which can lead to creeps targeting their attack on you.
If you are jungling with summoners always pay attention to the HP of your units. If one of them dies the next target for attack will be determined by the neutral creep.

^This. Basically, whenever you attack a ranged creep that isn't currently being attacked by something else, it will switch targets to you. This is also true for waves.