Remember participles? 

Verbal adjectives, they agree with some noun or pronoun (as their subject) but may take their own object or other predicate: translate with '-ing'.

1) The easiest to form are the middle parts.:

just replace endings with  -όμενος,  -η,  -ον

δέχ-ομαι --> δεχ- όμενος,  -η,  -ον,  γίγν-ομαι  -- γιγνόμενος,  -η,  -ον

So '(the one) receiving the money' is [ὁ] δεχόμενος τὸ ἀργύριον

or ὁ τὸ ἀργύριον δεχόμενος

(the one) 'Becoming great' [ὁ] μέγας γιγνόμενος

 Of course, participles can be singular or plural, in any case:

We heard/listened to (the man) receiving the money; ...the one becoming great:

 ἠκούσαμεν [τοῦ ἀνδρὸς] τοῦ δεχομένου    

(or τοῦ τὸ ἀργύριον δεχομένου]

ἠκούσαμεν [τοῦ ἀνδρὸς] μεγάλου γιγνομένου

We obeyed (+ dative)...

          ἐπειθόμεθα  [τῷ ἀνδρί] τῷ δεχομένῳ...  (or τῷ τὸ ἀργύριον δεχομένῳ]

          ἐπειθόμεθα  [τῷ ἀνδρί] μεγάλῳ γιγνομένῳ.

2) The present active participles are formed

like 'old man' γέρων,  γέροντος  in the masculine;

feminines end in -σα,  -σης

γραφ-ω  ---> γράφ-ων,  γράφοντος....γράφ-ουσα  writing

γιγνωσκ-ω-->γιγνώσκων,  γιγνώσκοντος ...γιγνώσκουσα,  --ούσης   learning

λαμβαν-ω ---> λαμβάνων,  -οντος...λαμβάνουσα,  -ουσης -- taking

First aorists are formed without augment, like πaς,  πᾶσα,  πᾶν [παντός,  κτλ.]

and generally convey the sense of finite or finished event, a single moment (whereas the present conveys ongoing action)

ἔγραψα--> γράψας,  γράψαντος...γράψασα,  -άσης  '(having) written' or 'writing (all at once)'

Practice with  πράττω,  ἔπραξα.... 

πέμπω,  ἒπεμψα...

Second aorists form their participles just like the present (but accent the ending)

ἔλαβον--> λαβών,  λαβόντος... λαβοῦσα,  -ούσης 

'(having) taken' or 'taking (all at once)'

Practice with  λείπω,  ἔλιπον ....

πάσχω,  ἔπαθον...

Athematic aorists are formed like the First aorists but without the -sa-:

 endings added directly to the vowel of the root:

γιγνώσκω,  ἔγνων  (root gno-) --> γνοῦς (from gno- + nts) γνόντος =

'knowing/having learned/ realizing"

 βαίνω,  ἔβην --> βάς (from ba- + nts) βάντος,  ...βᾶσα,  βάσης, 

'(having) gone, stepped'

If you remember these, the -μι verbs are easy--because they, too, are athematic (without the o/e connecting vowel of regular verbs). You add participle endings directly to the vowel of the root:

τι-θη-μι --> (reduplicated present, root the-+ nts)   τι-θείς,  τιθέντος, ...

τιθεῖσα,  τιθείσης...'putting/placing'

 ἔθηκα  --> (root the-+ nts)  θείς,  θέντος  (without reduplication)

= '(having) put/placed'

δι-δω-μι --> (reduplicated present, root do-+ nts)  δι-δούς,  διδόντος...

διδοῦσα,  διδούσης... giving

 ἒδωκα  --> (root do-+ nts)  δούς,  δόντος  (without reduplication)

= '(having) given'

ἵ-στη-μι --> (reduplicated present, root sta-+ nts), ἱ-στάς,  ἱστάντος...

ἱστᾶσα,  ἱστάσης

Second aorist, ἔστην --> (root sta+ nts) στάς,  στάντος, 

'(having) stood' intransitive

Don't forget first aorist,  ἔστησα -->  στήσας,  στήσαντος...

στήσασα,  στησάσης '(having) made stand/stop' transitive

3) Then there's always the future: for some active verbs the future is middle

 βαίνω,  βήσομαι -- βησόμενος,  -η '(being) about to go'

λαμβάνω,  λήψομαι -->ληψόμενος,  -η 'about to take'

μανθάνω,  μαθήσομαι-- μαθησόμενος,  -η,   'about to learn'

Practice with ἀπο-θνῄσκω....

-μι verbs have regular futures:

τίθημι,  θήσω --> θήσων,  θήσοντος...θήσουσα,  θησούσης

δίδωμι,  δώσω -- δώσων,  δώσοντος...δώσουσα. κτλ

ἵστημι,  στήσω-- στήσων,  στήσοντος...στήσουσα,  κτλ

Remember future participles are especially useful with ὡς  to express purpose = so as/in order to

"They listened to the old man (in order) to learn the truth"

    ἤκουσαν τοῦ γέροντος ὡς τὴν ἀλήθειαν γνώσομενοι  (plural nom. to agree with subj.)

Practice completing the sentence, "They listened..."

...(in order) to receive the money

... (in order) to become great