Di tres les (the third lesson) of Goilo's book covers several important topics.
Verbs that do not use ta to indicate the present tense: tin, por, sa, konosé, ke, mester, and verbs that might or might not use ta: debe, gusta, kosta, bal, stima, etc.
Using esta to form exclamations:
Esta un cas grandi : What a big house!
Esta un homber loco : What a crazy fellow!
Goilo gives some examples of using por, ke, mester in the past tense. I'm not sure his explanation is entirely clear. He gives both mi tabata sa mi les and mi a sa mi les as equivalents for "I knew my lesson." Is there a difference in meaning? In my own studies I have noticed that tabata sa is much more common than a sa.
Goilo also mentions that cu (ku) is used instead of i to conjoin personal pronouns: nan cu nos rather than nan i nos.