How do you form a gerund?

2 general rules: 1) if the verb ends in "-ir" or "-er", remove the "r" and add "-iendo". 2) if the verb ends in "-ar", remove the "r" and add "-ando". If there is a vowel formation such as "-eie-" in the middle of the word or "-ie" at the beginning of the word, the "i" becomes a "y".