1. There's 2 schools of thought. Some say Bliz 3 to start because it allows you to cast Thunder II while still regenning mana and then Fire III casts faster so you get rolling faster once the cast time is over. The other school of thought is to pre cast Thunder 3 at the start of the fight and then roll into Fire III to get going. The latter is traditionally used when you plan on using Raging Strikes into your flare->convert combo after you fire out as the extra time on the thunder dot allows you to go about the full combo before it runs out while thunder 2 would cause it to run out earlier (assuming no thundercloud procs ofc).
2. Hold right mouse button, turn your character to face the target as it moves so you don't break line of sight.