Position yourself further back than you would normally be, keep the inputs as smooth as possible & the bike as upright as possible.
Depending on how much traffic there is, how it's flowing & how heavy the rain is the centre of a lane may still be fairly dry. Otherwise take up an off-side position to be able to see traffic ahead & be seen by oncoming drivers.
Take the widest line possible if you're cornering to keep as much of a contact patch, but watch out for
Painted lines, wet leaves (they're only slightly grippier than oiled ice
), shores (drains, manhole covers, tram tracks ect.) will be slippery.
Diesel / oil will generally give a shine, avoid it.
Standing water can be a lot deeper than it looks, I was out with a buddy when we got monsoon levels of rain (I'm Irish, I commute on the bike daily so I'm well used to riding in rain. If I only went out on dry days I might get out once or twice a year
) I was leading the way back a well known stretch of road & went through a puddle that I thought should be about an inch deep, it was actually in a dip & was about half way up my boots
(after that I let my mate on his F650 GS take the lead)
If it looks like it will be a quick downpour take cover until it passes, if it's down for the day HTFU (Harden The F*ck Up) and keep going