1. Normally verb infinitive +-ing: work- working, watch- watching
2. When the verb ends in -e, this -e es dropped before -ing: write- writing, live- living
EXCEPTIONS: after verbs ending in -ee: see- seeing, agree- agreeing
3. -ing is added to a verb ending in -y without affecting the spelling of the verb: carry- carrying, study- studying.
4. When a verb of one syllable has one vowel and ends in a single consonant, this consonant is doubled before -ing: hit- hitting, cut- cutting.
5. Verbs of two or more syllables whose last syllable contains only one vowel and end in a single consonant double this consonant if the stress falls on the last syllable: ad'mit- admitting, be'gin- beginning, BUT 'open- opening.