Imperative is formed with suffixes. Suffixes differ depending on a category of a verb. We will not discuss all the details (slight differences depending on stem of a verb) and will encounter just suffixes and not examples:
Examples of imperative see in Verb Paradigms.

Imperative suffixes for vta verbs:

Imperative suffixes for vti verbs:
 

Imperative suffixes for vai verbs:  

We'll take for example two vai verbs: namadabi (he sits) and biindige (he enters):

In Prohibitive Imperative a prohibitive word gego (don't do!) and special suffixes are used. Examples of Prohibitive see in Verb Paradigms.

Prohibitive Imperative suffixes for vta verbs:

Prohibitive Imperative suffixes for vti verbs:

Prohibitive Imperative suffixes for vai verbs:

If a verb ends in a consonant, "k" in a suffix changes into "g": /-gen/, /-gegon/.

Examples:

gego namadabi-ken � don't sit (you s.)!
gego namadabi-kegon � don't sit (you pl.)!
gego namadabi-sidaa � let's don't sit!

gego dagoshin-gen � don't arrive (you s.)!
gego dagoshin-gegon � don't arrive (you pl.)!
gego dagoshin-zidaa � let's don't arrive!

"Yes/no" questions, which need "yes" or "no" answer are formed using special question marker - a word ina or na. It always stands after the first word in a question:

giwiisin ina? = are you eating?
giminikwe na? = are you drinking?
ginamadab ina? = are you sitting?
gigii-anokii na bijiinaago? = did you work yesterday?
giwii-izhaa na adaawewigamigong waabang? = will you go to the store tomorrow?

Negations are formed with a word gaawiin = «no, not» and a negative suffix /-sii/ or /-zii/ for vai and vta, /-siin/ or /-ziin/ for vti and vta, /-sinoon/ or /-zinoon/ for vii. A consonant in a suffix depends on a stem ending - 's' after a vowel and 'z' after a consonant:

gaawiin niwiisinisii = I'm not eating
gaawiin niminikwesii = I'm not drinking
gaawiin ningii-anokiisii bijiinaago = I didn't work yesterday
gaawiin niwii-izhaasii adaawewigamigong waabang = I won't go to the store tomorrow

Negative suffix is added at the end of a verb in singular. But in plural it is usually put before plural suffix for vai verbs or between singular and plural parts of a suffix of vti-s and vta-s:

gaawiin wiisini-sii-wag = they are not eating
gaawiin niwaaband-an-ziin = I don't see it
gaawiin niwaaband-an-ziin-an = I don't see them
gaawiin niwaabam-aa-sii = I don't see him
gaawiin niwaabam-aa-siin-aan = we (exc) don't see him

Questions with words: who, what, when, where, why, etc are formed in a different way than "yes/no" questions. Verbs in these questions stand in B form (or conjunct order). Initial vowel change in B form (changed conjunct) occurs in this case:

Note. Though B form with an initial vowel change is used in different regions usually in the same cases, it could be formed differently in different subdialects. This rule of an initial vowel change occurs in its complete form only in Minnesota Ojibwe. In other subdialects it is very much reduced and often replaced with other grammatical changes (preverbs e-, gaa-, etc.)

Initial vowel change affects also past and future tense prefixes: /gii-/ changes into /gaa-/, /ga-/ into /ge-/, and /wii-/ into /waa-/. Initial vowel change affects the first syllable of a verb, making no difference of what this first syllable actually is - tense prefix, preverb or a verb itself.

aaniin ezhinikaazoyan? = what is your (s) name (how are you called)?
aaniin ezhinikaazod? = what is his/her name (how is s/he called)?
aandi ezhaayan? = where are you (s) going?
aaniish pii gaa-dagoshing? = when did s/he arrive?

aaniin = what, how
aandi = where
aandi onji = where from
aniish pii = when

In answers A form (independent order) is used:

aaniin ezhinikaazoyan? - ojiig nindizhinikaaz
what is your s. name? - my name is Marten

aaniish pii gaa-dagoshinan? - ningii-dagoshin bijiinaago
when did you s. arrive? - I arrived yesterday
 
Note. Questions with 'where'.
In Ojibwe verbs can contain so called relative roots, which always show initial vowel change in B form. Izhi- and onji- are most often used examples of such roots. These roots force initial vowel change of a verb in B form.
Questions with 'where' (despite other wh-questions) don't need initial vowel change in a verb (B form without initial vowel change is used there). But in these questions mostly verbs with relative roots are used. So initial vowel change occures in where-questions very often. Though it is not a grammatical rule for where-questions, but a result of using words with relative roots.

First of all here is an excerpt with short linguistic explanation of obviative:

"Obviation is a grammaticized system of organization in which 3rd persons are ranked in prominence, and where this ranking has consequences for the morphosyntax.

"In Algonquian all third persons are ranked in prominence. The most prominent 3rd person in the span is called the PROXIMATE; all others are called OBVIATIVES. If there is only 3rd person in the span, it will, by default, be the proximate. If there is more than one, one will be the proximate; all others will be obviative. Proximates occur whenever there is a 3rd person. Obviatives arise only in contexts involving multiple 3rd persons. Given that multiple 3rd persons must be ranked in obviation status. Three factors emerge as relevant, one semantic (a), one syntactic (b), and one pragmatic (c):

a. Animates outrank inanimates; humans generally outrank animates. (including vii verbs obviative - not discussed here - weshki-ayaad)

b. A genitive outranks its head. (= 3rd person possessive - weshki-ayaad)

c. A more topical 3rd person outranks a less topical one." (Judith Aissen)

We will encounter two last cases (b and c) only in these notes and will do it upside down, so -

Obviative is a change of vta verb, an animate noun (and animate demonstrative pronouns and verbs, used with that noun) which are used with 3d person animate subject. Because of this change obviative is sometimes called the 4th person. Obviative appears:

1) If an animate subject stands in 3d person (singular or plural) and takes a vta verb and an animate object (= does something with any animate object). Then both vta verb and object (and demonstrative pronouns and verbs, used with the object) change their forms. This changed form is called � obviative.

2) If an animate noun in possessive form belongs to a possessor, which stands in 3d person (singular or plural). Then this noun (and demonstrative pronouns and verbs, used with this noun) change their form into obviative.

Nouns and verbs in obviative take special suffixes. Demonstrative animate pronouns in obviative are changed into plural inanimate demonstrative pronouns regardless to real number.

Noun obviative suffix is /-an/, or /-n, -yan, -wan/.

There is no fixed word order in sentences in Ojibwe language. Both subject and object could be placed before or after a verb freely. The main sense of obviative in this case is to distinguish a subject (main, proximate third person) from an object (other, obviative third person), cause if both of them are in 3d person the verb could belong to either of them.
In the next incorrect sentence with no obviative it is absolutely impossible to tell where is a subject and where is an object:

x nimbaabaa o-noondawaan ma'iingan x [x my father he-hears-him a wolf x]

Obviative suffixes solve this problem easily:

nimbaabaa onoondawaan ma�iinganan = my father hears the wolf. 

nimbaabaayan onoondawaan ma'iingan = the wolf hears my father. 

nimbaabaa � my father (no obviative)
omaamaayan � his mother (obviative)
nimbaabaa omaamaayan � my father's mother

White Eagle Soaring: Dream Dancer of the 7th Fire