... consonants on gerund and past simple of regular verbs. Can anybody refresh me those? Or maybe there's already a thread about it which I cannot seem to find...

Thank you.
One rule is to double the consonant to preserve the short vowel sound:

cite - citing - cited -- the long vowel sound is preserved.

fit - fitting - fitted -- the short vowel sound is preserved.
1. Verbs which end in a single consonant preceded by a single vowel in a stressed syllable double the final consonant.

wed - wedding - wedded
hop - hopping - hopped
occur - occurring - occurred

Note: 'x' is not doubled.

mix - mixing - mixed

Note: 'c' is not doubled. Double 'c' is written as 'ck' instead, regardless of the stress pattern of the syllables.

picnic - picnicking - picnicked
frolic - frolicking - frolicked

2. No doubling in the others.

More than one consonant at the end:
want - wanting - wanted
thirst - thirsting - thirsted

Final single consonant not preceded by a single vowel letter:
cook - cooking - cooked
fear - fearing - feared

Final syllable not stressed: (British English doubles in this case.)
travel - traveling - traveled
worship - worshiping - worshiped

3. Verbs which end in silent 'e' drop the 'e' before adding 'ing' or 'ed':

hope - hoping - hoped
invite - inviting - invited
move - moving - moved

There are a few exceptions (-ing form):

dye - dyeing - dyed
singe - singeing - singed
hoe - hoeing- hoed

Note that 'i' becomes 'y' in these 'ing' forms:
lie, die, vie - lying, dying, vying - lied, died, vied

4. Final 'y' changes to 'i' only before 'ed', not before 'ing':

pity - pitying - pitied
worry - worrying - worried

CJ