Use head auto snap.
Draw your mainline first, if you can, then drop your valves right onto it.
When you have a bunch of areas exactly the same, like square tree wells or planting areas in pavement, do your head/bubbler/drip area polyline layout, then copy and paste. For example, I'll put three bubbler symbols around a tree, then just copy them over to all the other similar trees. Do this BEFORE you draw and size the pipe.
Use "copy along a line" and "copy along a polyline" a LOT.
For polylines for drip areas, copy them over from an xref, if you can. Get good at breaking and joining polylines if you need to divide up large areas. I have a client that shows hydrozone areas on their plans, so I just copy those p-lines over into my drawing.
Use Verify Laterals frequently to catch pipe hops and unpiped emitters as you work, instead of saving it all for the end. This is very helpful on large projects.
Size your main line frequently as you work to make sure you stay within the hydraulic parameters.
For page layouts, in model space I'll put a matchline on a non-plot layer and use that to line up my viewports in paper space. Then I'll use the LandFX matchline in paper space.
I like to screen back the plant symbols in the xref'd planting plan, so I can see tree locations, etc. It helps, obviously, with placing tree irrigation, and, for lateral pipe routing, so I'm not showing pipe under a tree root ball.
That's what I can think of for now.
Who else has tips?