For when you launch the new website, Google have a change of address tool: 
https://support.google.com/webmasters/answer/83106?hl=en

As mentioned, 301 redirecting the exact old page to the exact same new page is the most important step. Plan ahead and map out your 301 redirects. You want to be sure of what's happening when the domain is transferred to give your rankings and traffic the best chance of remaining intact (or even increasing, which I've seen with some website redesigns).

I think you can change your Twitter handle more than once. If you have a good existing following I'd recommend updating your existing profile to the new handle, and (if possible) re-registering the old Twitter handle at another account - linking in the bio to your new Twitter account. That'll make sure you retain some of the link authority your current Twitter profile has built up and ensure people can still find you through any old links. I think custom Facebook URLs can be changed once.

I actually wrote a site migration guide last week, there should be a few points in there you'll find useful: insideonline.co.uk/website-migration-guide/

I see the value of associating anchor text with content links rather than navigation, but I agree with EGOL more than Ryan on this one. What if users are viewing the site with CSS disabled? Maybe because it's easier to view with a screen reader for blind/partially sighted people - it's not very user-friendly having the main navigation links only at the bottom is it?

That could be an issue. Was it targeted to the UK before?

Looking further into it, the Penguin updates throughout the year (the first in April)  don't match directly with the timing of drops you mentioned, but some of your "one direction" exact match anchor text links could have been devalued. The site-wide footer link here for example, on a completely unrelated website (that's a big no-no in Google's eyes): http://www.tapshop321.com/blog/

How about the explosion in popularity of the band? Your Domain and Page Authority is lower than most of the results on the first 3 pages. This is worldwide but illustrates the point - there will be a lot more competition from other sites now: http://www.google.com/trends/explore#q=one%20direction&cmpt=q

The 100 links per page limit isn't much of an issue these days. As long as Google can crawl your menu links (e.g. the menu is not hiding behind JavaScript) and you don't have hundreds and hundreds of links, it should be fine. Other than that you should do whatever is best for the customers rather than thinking about the search engines; personally I was a little overwhelmed by some of the menus on your site, but then again I hadn't taken note of what your site was selling, so at first didn't know what I was looking at.

It'll just look spammy. Exact matching anchor text seems to be becoming less effective anyway, and Google is good at looking at the context links are placed in, so if a Spanish link is inserted into otherwise English text that will probably look dodgy. And if you're targeting Spanish search engines, links from other countries have less value anyway.

I'd say a DMOZ link is worth applying for but not worth a bead of sweat if you don't get accepted/moderated.

It's the overall variety of a link profile that counts. If you get links naturally you'll have a mix of follow and nofollow, URL-match, branded, non-branded anchor text and some keyword match thrown in, homepage links and deep links, social and non-social...

I like the phrase "If Google did not exist but the Internet did, where would you get links?"

In answer to your original question, I agree with Doug. if you're offering a product it's a good idea to offer it to influential bloggers that your target audience visits for free, in return for an unbiased review and link. But if you're just starting out don't go for the biggest bloggers as they probably get inundated. If your product is great the most influential will pick up on it through some of the 'smaller' blogs.

Check out the free Xenu Link Sleuth and this post: http://www.seomoz.org/blog/xenu-link-sleuth-more-than-just-a-broken-links-finder

I haven't used it myself (yet), but Screaming Frog could help as an alternative, though the full version is paid. This post compares the two: http://www.seomoz.org/blog/crawler-faceoff-xenu-vs-screaming-frog

Yes, use hyphens for filenames, and lower case.

"I have an about page with the url "www.heartwavemedia.com/about" and the SEO title San Francisco Video Production | Heartwave Media | About"

I'd say the URL you have already is perfect. For the "SEO title" (title tag) I'd go with "About Heartwave Media" - the unique part of the title tag should be at the start.

Think about what is best for the human visitors to your website, and not the search engine crawlers. People expect an "about" url to be at www.example.com/about or www.example.com/aboutus - it's also memorable and easier to type in. I've always said this is the best way, and Google is getting smarter at ranking content that is useful for searchers: http://moz.com/blog/be-the-result-that-google-wants-to-rank

If every URL on your page had "san-francisco-video-production-" in it, it's not user-friendly, and it looks spammy, so to Google it's definitely going to look spammy, either now or at some point in the future.

Also be aware of keyword cannibilisation. You want search engines to know your website is about video production, but you don't want to confuse them over which page they should rank highest. This is an old article but still relevant: http://moz.com/blog/how-to-solve-keyword-cannibalization  It's fine to mention "video production" and variations of that theme throughout your website, but be aware of the cannibilisation issue. If you think it's most important to rank for "San Francisco Video Production" then that should be your homepage title, arguably with your brand name at the end.

I'd more than likely go for something different on each page. Make sure you're describing the page content accurately in the title.

You don't need to include your brand in any of the titles. Some people believe it's better to have the brand name, some don't. Amazon for example - they're a strong, well known brand - so it makes sense to include the brand name as it can encourage click throughs from Search Engine Results Pages (SERPs). For a business like yours I wouldn't think it'd make a big difference either way. As you're targeting local customers, it could result in extra exposure for your brand name if you include it, though the longer a title tag the less emphasis is given to each keyword in the SERPs - so that's a small reason not to include it. If you go back to what I said about thinking about the user, then you'd have the brand name on the homepage and about page for definite, but other pages - it probably doesn't matter so much. As you noticed on another thread, sometimes Google will add your brand name anyway! You could also consider how people's bookmarks display, but again I'll say - don't worry about this too much!

In terms of your question about speed, there are a few resources you can put your URLs into that will give  you feedback and recommendations. Here are 2:
tools.pingdom.com/fpt/
http://developers.google.com/speed/pagespeed/insights/

You can optimise titles for both. It's best to have your prime keyphrase near the beginning of the title - and make sure the title is not too long.

The way you suggested does make it look like you're just stuffing the keywords in for the sake of it though...again it depends on your keywords but something like this would look more natural with the downside of not having one of the phrases nearer the start:

"Green Apple seller: the best Green Apples"

"If they are only going to be visible in the SERPS and you know they are going to be cut off then they will never see the words after the cut-off point."

That's not always true, but I see you question it later on - I have seen a few examples where people have used long meta descriptions with the intention of the SERPs displaying something different depending on the search made. Here's one I've just found: http://sharkseo.com/whitehat/meta-descriptions/ - though I've just done a search and I got the same meta description ("Dave is a freelance SEO consultant...") for both suggested searches.

If Google doesn't think your meta description is appropriate there's always a chance they'll replace it with something else on your page or the description from DMOZ.

You should definitely not add the ellipsis yourself, what if the length displayed is changed for example? I'd just ensure your first 155ish characters are well-written in a way that entices users to want to click through.