I have a bunch of heads for a number of different situations, but let me take you through the ones I use the most - and why.
I have two floaters that I use most of the time when fishing floating lines (which I do maybe half the time). Both weigh 14 grams, which suits me perfect. The rod will easily handle both 15 and 16 grams, but I feel that 14 grams really keeps the rod crisp and fast. One is 9,2m long and the other is 10,8m long. It's wind and conditions (room for backcast) that determines which one I use.
To complement those I have a really short one (6m), which is handy in really confined spaces, where it, coupled with a monofilament shooting line, gives a reasonalbe distance.
I also have intermediate (slow and fast) and they are the ones I use the 50% of the time when either fishing faster or over deeper water. And to add to those, I also have a sink 2 and a sink 4, which I use over really deep water (for mackerel, for instance), but that's rare and actualy only on two different locations.
On the HT 890 I use 18 grams, and like the 6, the 890 wirl also easuly handle 19 or 20 grams, but again, I like to preserve that crisp and fast blank and maybe keep things just a tad on the light lside.
I have more or less the same setup for the 890 for the salt, but for pike, I add a short 20 gram (heavier lines cast bigger flies) 8m shooting head and a selection of intermediate, sink 3, and sink 6.
The handy wallets in the pic keep that heads handy and organised.
For both rods I can really recommend Scientific Anglers Saltwater and RIO Gold - they are the only two WF-lines I use on the rods.
Later, I'll elaborate on lines (and shooting heads) for the HT 490 (it feels really "zippy" with the right head).
Have a great weekend!
PS - 6 hours of fishing day before yesterday in the pontoon boat yielded one 38cm sea trout :-).