Participle patterns
Separable verbs insert ge- after the prefix: eingekauft. Inseparable prefixes such as be-, ver-, er- do not add ge-. Verbs ending in -ieren also have no ge-.
Understand the idea
Past participles have several formation patterns. A regular participle often has ge- plus the stem and -t, but separable prefixes, inseparable prefixes and -ieren verbs change that pattern. Strong verbs commonly use -en and may change their stem vowel.
Build it step by step
Place ge- after a separable prefix. Do not add ge- to ordinary inseparable prefixes such as be-, ver- or er-, or to verbs ending in -ieren. Verbs with stems ending in -t or -d often need -et in a regular participle. Strong and mixed participles need their own learned forms.
See it in a sentence
Ich habe Brot eingekauft.
Wir haben Berlin besucht.
A useful memory aid
Group verbs by pattern before learning individual exceptions. Compare gemacht, eingekauft, besucht and studiert as four different starting models.
A common trap
Avoid adding ge- mechanically to every verb. Also remember that an irregular vowel change does not tell you by itself whether the participle ends in -t or -en.