Basic question on Imperative
Mina-san!

Mou ichido tetsudatte kuremasu ka? (That was supposed to mean: "Can you help me again?" I'm sure you can't combine it like that, but it's all I know for now; gomen nasai!)

I'm trying to get a (very) basic grasp on verbs and their conjugations. I ran across this standard phrase on a podcast: "Ganbatte kudasai!" So I resolved to explore just the Imperative a bit for now, for which someone handed me the following rule:

"Ru-verbs are easy because they all follow the same rule for forming the imperative, as you can see: make the -masu form, eg. taberu - tabemasu, then take off ‘masu’ and put ‘te’ instead - and that’s it."

So, after some searching I found that 'taberu' and 'miru' are basically Ichidan verbs (ending in -ERU and -IRU), that conjugate differently from regular Yodan verbs, like those ending in -RU, such as 'ganbaru,' right? Like:

ganbaru - ganbatte
suwaru - suwatte

Then I looked up some -ERU and -IRU forms, like:

miru - mite
taberu - tabete

I almost felt like I was beginning to understand it, when I ran into:

hashiru - hashitte

Itai-yo! (Ouch!) Where does the extra T come from, all of a sudden? I expected "hashite".

I would be most grateful again if someone would explain this to me. And I apologize, also again, for asking such newbie questions.

Question

Basic question on Imperative
Mina-san!

Mou ichido tetsudatte kuremasu ka? (That was supposed to mean: "Can you help me again?" I'm sure you can't combine it like that, but it's all I know for now; gomen nasai!)

I'm trying to get a (very) basic grasp on verbs and their conjugations. I ran across this standard phrase on a podcast: "Ganbatte kudasai!" So I resolved to explore just the Imperative a bit for now, for which someone handed me the following rule:

"Ru-verbs are easy because they all follow the same rule for forming the imperative, as you can see: make the -masu form, eg. taberu -> tabemasu, then take off ‘masu’ and put ‘te’ instead - and that’s it."

So, after some searching I found that 'taberu' and 'miru' are basically Ichidan verbs (ending in -ERU and -IRU), that conjugate differently from regular Yodan verbs, like those ending in -RU, such as 'ganbaru,' right? Like:

ganbaru -> ganbatte
suwaru - suwatte

Then I looked up some -ERU and -IRU forms, like:

miru -> mite
taberu -> tabete

I almost felt like I was beginning to understand it, when I ran into:

hashiru -> hashitte

Itai-yo! (Ouch!) Where does the extra T come from, all of a sudden? I expected "hashite".

I would be most grateful again if someone would explain this to me. And I apologize, also again, for asking such newbie questions.

Answer

As far as I know, these are simply exceptions and there's really no way of telling them apart except going the memorize route. The good thing however is that they really are few and far in between; it's basically nothing compared to e.g. the list of irregular verbs in English. :)

Answer

Actually, not all verbs ending in -IRU or -ERU, fall into ichidan group. Among regular godan(it's godan, not yodan), there are some verbs that end in -IRU or -ERU just by chance. 
But the good news is, the exception list is not too long, as noiz-san above says. Here is some examples.
Kaeru(go back)
Hairu(enter)
Shiru(get to know)
Hashiru(run)
Kiru(cut)
Iru(need)

If you know "-nai " form of the verb, it'd be easier to distinguish godan or ichidan. All ichidan verbs become -enai or -inai, while all godan verbs become -anai.

Answer

Hi Mark, there's a good explanation at 
http://en.wikipedia.org/wiki/Imperative_mood

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