This might seem obvious but a good reminder either way
Now I'm not a super long term veteran, or really high elo but I've even seen people do this at too many elos. If you see the enemy jungler in a bush because it's warded. Do not fire a skill shot at him, and for the love of Cthulhu do NOT type in all chat "Hurr Hi
" because it's not only kind of obnoxious but typing right in the middle of your lane is just stupid, especially if the jungler is right there. If they thought "screw it" and went on you in the middle of typing, well you were just made a fool weren't ya?
Point is, you WANT them there if you know they are there. Act like you don't know, but don't give them a chance to go in, make it look like they might have a chance if you can. Keep them there, waste their time. At best, all they're doing is soaking up xp, but beyond that they are accomplishing nothing. Ideally this gets pressure off your other lanes, let's your own jungler set up a gank elsewhere, or steal their buff, counter gank them before they can even gank.
All those opportunities are lost when you go /all Hi enemy jungler (translation; Yes it's warded, don't forget to sweep it on your way out, no, no need to thank me for the extra time and money I saved you)