1. FOR THINGS THAT HAPPEN REGULARLY WHEN A CERTAIN CONDITION IS MET
   1. Use si + present indicative + the present indicative
      1. Si llueve (if it rains) no salgo. ( I don't go out.)
2. TO GIVE AN ORDER DEPENDENT ON THE CONDITION BEING MET (IN THE PRESENT) - VIEWED AS LIKELY OR QUITE POSSIBLE.
   1. Use si + present tense + imperative/command form
      1. Si llueve (If it rains) no salgas! (don't go out!)
3. FOR EVENTS THAT WILL OCCUR (IN THE FUTURE) IF THE CONDITION IS MET (IN THE PRESENT)
   1. Use si + present tense + future tense
      1. Si llueve (If it rains) saldré (I'll go out)
4. FOR THINGS THAT ARE LIKELY OR ARE CONSIDERED LIKELY TO TAKE PLACE
   1. Use si + present indicative + the present indicative
      1. Si sube el precio, no lo compramos. If the price goes up we won't buy it.