Substitution/elimination

primary with a strong base/weak nucleophile (ex: bulky)

E2

secondary with a strong base/weak nucleophile (ex: bulky)

E2

tertiary with a strong base/weak nucleophile (ex: bulky)

E2

primary with a strong base (pka>12)/strong nucleophile ex: HO-, MeO-

SN2 for the most part

secondary with a strong base (pka>12)/strong nucleophile ex: HO-, MeO-

E2

tertiary with a strong base (pka>12)/strong nucleophile ex: HO-, MeO-

E2

primary with a weak base/strong nucleophile (ex: I-) pKa<12

SN2

secondary with a weak base/strong nucleophile (ex: I-) pKa<12

SN2

tertiary with a weak base/strong nucleophile (ex: I-) pKa<12

SN1

tertiary with a weak base/weak nucleophile (ex: CH3OH)

SN1, E1 if high temp

SN2 product stereochemistry

only inverted product formed R→S

E2 product stereochemistry

both E and Z are formed unless the B carbon where the hydrogen is removed only has one hydrogen

SN1 product stereochemistry

both S and R are formed with generally more inverted product

E1 product stereochemistry

both E and Z formed (with more of the largest groups on opposite sides of the double bond)