right STI levers for the rear gears.
Left STI levers for the front gears.
+ when you're shifting, don't cross the chain i.e.(Biggest diameter front cog & Biggest diameter rear cog combination).
To avoid this, for example when you're in the biggest diameter front cog, don't shift unto the last two rear cogs nearest to the rear wheel. Instead shift the front gear to the smaller gear if you must access those last two gears.
Summary: For each front gear, there are two back gears you should avoid using.