Actually, this is one of the more important skills of the game for caster/hybrid types. (More important for casters obviously, but still quite essential for a Ranger as well).
The skill is in knowing what to have loaded for which occasion.
Which obviously also means having a thorough understanding of how your spells work, what they do and what they cost (not PP, in terms of time, mana and opportunity).
This is an enormously broad subject and not one that can be covered in a short post here. Really it is something you need to study experiment with and practice.
However (
, my first tip is to settle on a sequence and then
always have them memmed in the same order. The time will come where you will need to be able to hit the right spell with a key stroke without time to think or look. It will need to be a reflex action.
Not a lot of good is going to come from diving for an emergency patch heal, only to find that you just snared yourself.
I
always have my fastest/best patch heal in slot 1, and always have my best root in slot 8 for example.
Second tip is to use the "saved spell set" facility. Right click on the button at the bottom of the spell gem window and you get a drop down window with the options to save and load spell sets. Use this to arrange a series of spell combinations that you will use in different tactical situations. Name them in a meaningful way. Then when you need to change a spell line up, right click the button and load the saved set you need for the occasion.
This works even with the need to swap in just a couple of spells, as it does not take up the mem time for spells that are already loaded.
If you are needing to lust swap one in a hurry, of course you can right click the actual spell gem twice to drop the old spell and bring up the drop down window to quick select the spell you need.
I keep one slot (no.2) as always my "hot swap" spell, so again in tactical situations I can swap in an alternative with the minimum of thought. (This is mostly on Celeni though, at higher levels a Ranger does not have too much need to make mid battle spell swaps, although beween battles I am oftem swapping in buffs for those poor deprived tanks
)
My Ranger line up usually looks like so;
Heal (always here, chloroblast)
Hot swap (Call of Fire proc buff)
Feet like Cat (so sue me, I
need that 5 AC) or Eagle Eye
Nuke (Calefaction)
Flame Lick (crowd control essential)
DoT (Drifting Death)
Snare (always here, crowd control esential)
Root (always needed, crowd control essential)
I have a "buffin" spell set and a "battle" spell set and a "standard" spell set. Celeni has a few more sets with emphasis on healing, nuking, or DoTs as the situation demands.