In novice Japanese classes (or at least the one I took a long time ago.), they expect you to translate the 「わたしは」 instead of dropping it. (assuming you are starting from an English sentence.)
I'd managed to get a whole bunch of red-marked corrections on one of my early homework assignments because I decided to go ahead and drop the 「わたしは」 instead of leaving them in. (I was taking the class primarily for the speaking and listening lessons.) This was despite the teacher being a native speaker.
The reason given was that the teacher has to be sure that the student knows what 「わたしは」 means. Assuming that a
novice student knows the nuances of when to drop the subject (or technically, "topic") is not a good idea, as most novice students probably do not have prior knowledge of Japanese. It's possible that the student may have neglected to put 「わたしは」 because he doesn't know how to translate "I will/I do/I am/etc."
Best if the OP checks with his teacher, but there's nothing grammatically wrong about appending わたしは to the beginning of a sentence all the time when the topic is about the speaker. Very awkward, yes, but there's nothing wrong.
If I recall correctly, when talking about meeting somebody at a specific place at a specific time, the preferred construction (ie: the "Textbook" example) was 「わたしは(Specific Time)に（Place)で(Person)にあいます。」 or 「わたしは(Relative Time)（Place)で(Person)にあいます。」 「げつようび（に 」 (On Monday) and 「ななじ（に）」 (At seven o'clock) are considered to be specific while relative time refers to a time period that is relative to the moment when you were speaking, such as 「きのう」(Yesterday) and 「あした」(Tomorrow)
「に」, when used to refer to time, has a meaning similar to the English "at", "in", and "on". In my class, the use of 「に」 was usually required for "specific time periods" and generally considered incorrect for "relative time periods". An exception was made for multiple "specific time periods" in a row, such as 「げつようびにななじに」, with the teacher asking us to write 「げつようびななじに」 instead. According to her, the former, while technically correct, is incredibly awkward, and the teacher can already see that the student knows how to use 「に」 properly since it was already appended at the end of 「ななじ」
The use of [ーとあいます。」 was discouraged because it was not taught in class yet. Generally, try to avoid using constructions that have not been taught yet, unless you have discussed it with your teacher or if the teacher knows your capabilities well.
When used to
indicate direction of motion, no distinction was made between 「に」 and 「へ」 (e.g. "にいきます" and "へいきます") The teacher actually encouraged the students to use 「に」 instead of 「へ」 since the latter has more specific uses (while 「に」 can also be used for other functions), so the student is less likely to make mistakes.
That said, the teacher did tell us that she preferred us to use 「へ」 if there's another 「に」 in close proximity, to make it easier to read.
There are slight differences between 「に」 and 「へ」, and Columbine was correct. The distinction was not taught in class because it's likely to confuse a novice learner of Japanese. If you are curious though, read on.
(Some basic kanji will be used. This is a 'check' of sorts, as I believe that the knowledge of these kanji is more important than knowing the subtle differences between 「へ」 and 「に] If it's too confusing to read, come back when you can read kanji comfortably.)
Technically, 「に」 implies arrival (or technically, "the state of being somewhere."), while 「へ」 implies direction of motion. The former places emphasis on the actor (the person doing the "moving") while the latter emphasizes the destination. For example:
私は学校に行きます。 I go to school. (and I will be there.)
私は学校へ行きます。 I go towards school.
Both of these have almost the same meaning, but the former implies "arriving at school", while the latter implies "heading towards the direction of school."
Despite the slight differences, I believe that most native Japanese speakers would not differentiate between the two anyway since both "arriving at school" and "heading towards the direction of school" is generally implied regardless of how the sentenced was phrased.
'though I suppose somebody 'crafty' could play with the words to come up with an excuse. AKA
"I did say that I was heading towards school, but I didn't say that I would stay there!"
Still not a good idea though.