Below is a great combo tool:
Play around with it, learn what combo fields you can do yourself and
start to learn what combo fields your team mates have in their builds.
Also get into the habit of declaring when you drop a combo field. The best way would be like this:
Mesmer = "Dropping Time Warp on the point."
A player who has studied that combo tool or combo fields will know that this gives Chaos
Armour as a combination and as a result would drop an ability (a
Warrior Batlle Standard, a Necro Putrid Mark) that gives it to all his
Warrior = "Dropping Fire field on Enemy X"
Although the warrior hasn't stated what the ability is, you will now
know 100% that burning is going down on Enemy X and as a result should
try and get some projectiles through it and onto them to stack Burning.
TL:DR = If you have abilities that switch boons for conditions or vice
versa, learn them. Everyone has combo fields and can use combo fields so
get reading and play with that tool. This isn't too long though, read
it all, learn it!