verbs If the subject of the sentence is first person, then the verb must be in what form?
This is a very ambiguous question. You have asked which "form" of a verb the first person subject will take. Let us clarify first.
English verbs have 6 tenses and 3 forms. The 3 forms are as follows:
Basic, Progressive, and Emphatic
The 6 Tenses are as follows:
Present Present Perfect
Past Past Perfect
Future Future Perfect
As the above post mentions, subject/verb agreement is always observed when conjugating verbs with their subjects (i.e. putting verbs in the proper "form" as you say)
Now, let us use a verb as an example - to learn and conjugate it in all its forms and tenses. Then, you can select which one answers your question as you will see which helping/auxiliary verbs are used with the main verb, learn.
Present Tense-I learn Present Perfect Tense-I have learned
Past Tense-I learned Past Perfect Tense - I had learned
Future Tense - I will learn Future Perfect Tense- I will have learned
Present Progressive - I am learning
Past Progressive - I was learning
Future Progressive - I will be learning
Present Perfect Progressive - I have been learning
Past Perfect Progressive - I had been learning
Future Perfect Progressive - I will have been learning
Present Tense - I do learn Past Tense - I did learn
[There are only 2 tenses in the Emphatic Form]
To continue this discussion, it is important to consider what import the sentence has. For instance, is the sentence supposed to convey something one is doing right now? Then, use the Present tense, Progressive form. [e.g. I am writing this.]
Or, is it meant to convey a regularly recurring action? Then, use the Present tense, Basic form. [I write often in my journal.]
Forming the tenses and the various forms of verbs involves using one of the principal parts of the verbs [present -learn, present participle-learning, past - learned or past participle-learned] These principal parts are used with the auxiliary verb to be in the progressive form and the auxiliary verb to have in the perfect tenses of basic form and progressive form.
Wow. Both previous posters have suggested plenty of information. I use a text called Daily Grammar Practice. This uses the same sentence every day for a week. Monday addresses the parts of speech for the sentence. Tuesday addresses the sentence parts. Wednesday addresses the clause(s) and sentence types. Thursday addresses capitalization. Friday addresses diagramming. Other mini-lessons are embedded in the sentence, and this arrangement is wonderful because each day builds on and reinforces the learning from the previous days.
The previous poster did give a lot of good information. Still, I wonder if agreeing with a first person subject ("I" and "we" are pretty much your only choices here) is your problem. As an English teacher, I see lots of students make mistakes between the 3rd person singular and plural. With all points-of-view, though, tense mistakes are made. Whether you say, "I danced" or "I had danced" has nothing to do with the subject, but rather the tense in which the paper is written and whether or not you are using a flashback.
The sentence must follow the subject-verb agreement pattern. If the subject is first person, like 'I', 'we' etc. the verb should be generally 'am', 'are' in the present tense (indefinite & continuous). But, if it is in perfect tense, the subject 'I' & 'we' would take 'have' after them. In past tense, 'I' would take 'was', & 'we' would take 'were', but in case of past perfect tense, they both would take 'had'. In case of future tense, they both can take 'shall' or 'will' respectively, but normally, they take 'shall' with them.
Hope this will help.