General etiquette for follow up email

How do one follow up in japanese for a previously email to a company/individual that have gone unanswered?

Generally? If you've set a sort of a deadline for the answer (such as RSVP by so and so date), you wait until the day after deadline and ask
首記の件、その後、いかがでしょうか。

If you hadn't set a deadline, you wait about a week after you sent your first email and write the same thing as above. You should paste the original email underneath that.

But this is the "general" etiquette/routine. Things may differ depending on the situation or relationship.

Hi Uco,

Thanks for the reply. Sorry about the confusion. I was actually trying to ask how I should write to them instead...

Wondering if below is good enough in a polite way for most situation?

お世話になっております。
あなたにお送りしたメールから一週間近くが経ちますが、非常に忙しいですか？
若しくは、メールに気付いていましたでしょうか？

Hi James,

You should avoid "anata." It's not the same thing as "you." You should also avoid "hijyou ni isogashii desuka?" since it sounds sarcastic.

Assuming this is a business email (since you've written o-sewaninatteorimasu), the following would be more appropriate.

お世話になっております。
○月○日付でお送りしたメールは
ご覧いただけましたでしょうか。
お忙しいなか恐縮ですが、
一度、ご連絡をいただけますと助かります。
よろしくお願いいたします。

Again, you should paste the original email you've sent.

I think there are also examples out there on the internet.

Thanks for clarifying Uco. :D

That is very helpful.

By the way, I got a reply.

Does 用意 means to ready?
Also, is ダウンロードできましたらご連絡ください。 means to contact once download is completed?...

Does 用意 means to ready?

It can mean that, but it depends on the context. Don't you have a dictionary?
http://eow.alc.co.jp/search?q=%e7%94%a8%e6%84%8f&ref=sa

Also, is ダウンロードできましたらご連絡ください。 means to contact once download is completed?...

Yes.

Thanks Uco.

I usually use google translate since they often list out vocabularies if they have multiple definition from a single english word... Though I guess the words listed may not work in all situations...

To say I have downloaded and thank you for the help, it is like this:

(something)をダウンロードできました。お手伝いいただき、本当に感謝しています。

For the second part, would any of the following works?

お手伝ってくれて、ありがとうございます
お手伝っていただいて、ありがとうございます。
お手伝って下さって、ありがとうございます。

For the second part, would any of the following works?

お手伝ってくれて、ありがとうございます
お手伝っていただいて、ありがとうございます。
お手伝って下さって、ありがとうございます。

No, because you can't use お with 手伝って. You can delete お and all three will work (except that くれて is sounds very casual). By the way, you can't say 手伝いいただき without the お though.

But a more professional way to say "I have downloaded and thank you for the help." You usually say:

(something)をダウンロードできました。お手数をおかけいたしました。

You should obtain a dictionary and a how-to book/site on writing business emails, if you're going to write similar messages in the future for professional use. Otherwise, you should hire a real-life translator.