First three principal parts of some verbs

In Mastronarde's book, there is an appendix to Unit Eighteen, listing the first three principal parts (present, future, aorist) to about 80 verbs. Here are a few that have been giving me trouble.

want, wish - βούλομαι, βουλήσομαι, ---
perceive - αἰσθάνομαι, αἰσθήσομαι, ᾐσθόμην
suppose - οἴομαι, οἴσομαι, ---
arrive - ἀφικνἐομαι, ἀφιξομαι, ἀφικὀμην
have as a custom - νομίζω, νομιέω, ἐνόμισα
inquire - πυνθἀνομαι, πεὐσομαι, ἔπυθομην
fall - πίπτω, πεσέομαι, ἔπεσον
flee - φεύγω, φεύξομαι, ἔφυγον
march, drive - ἐλαύνω, ἐλάω, ἤλασα
praise - ἐπαινέω, ἐπαινέσω, ἐπῄνεσα

Typing in Unicode Greek

Tips here, along a useful keyboard map.

ὠφέλω, ὠφελήσω, ὠφέλησα - first 3 principal parts (present, future, aorist) "help," from which is derived the name Ophelia

sympathetic nasal

There's a verb root (that's even more basic than a "stem" right?) "puth" ... now in the present, it gets "-an-" added to make up the stem, along with a "sympathetic nasal" before the "th." So "puth" becomes (in the present) "punthan-xxx." And other principal parts are clearly derived from "puth," rather than "punthan-." In other words, the present tense (which we naturally take as the basic, most primitive version) has evolved away from the root, while the other principal parts have stayed closer to it.

It's also called "nasal infix."