What paid add or perhaps linkexchange gave your site a boost?

I was wondering what 'special' add in for example a paid directory or paid advertisement or even a linkexchange really boosted:

1) Searchengine position in the mayor searchengines.
2) Google PR.
3) Visitor count.
4) Sales.

Or a combination of those. At this moment i have nothing to complain, iam even still in the first phase with online marketing (free directories and speciality sites submission) afther this i'l move up to the next 4 steps. The second step which will be soon is to buy advertisement space, i know a few places where to place my add already but i was wondering what really helped you guys, so i perhaps have some options to consider.

My site is mainly focussing on business design services, varying from webdesign to brochure printing.

No single link really boosted our rankings, etc...

Just try to get a lot of quality backlinks - then you will see results.

Deffinitely get into DMOZ though.

Make connections with other webmaster's that have similar content and watch your rank grow!

Good contents: articles, guides, online tools, FAQ, etc. I just create them and free backlinks come: three ODP listings (even without asking), links from good PR pages, partnering requests, etc. Of course, SE rankings are very good for many keywords.

My main site is an informational ad-free web site that I (indirectly) use to "push" secondary commercial sites. Commercial sites have decent rankings too.

I also send (and sell) themed traffic to other sites.

To reply to your question: good related backlinks have helped me for sure. I never do link exchanges, but sometimes I ask for a free link.

I understand you can't just be in the top by buying or exchanging a few links. Iam working all the way around to get as many links as possible, i've just started doing this and i know it's a long way. But i was wondering if there was a potential link one of you received that really boosted something. For example when you paid for a link or add and didn't expect mutch of it but instead it send you hundreds of visitors, or perhaps you bought or exchanged a link that brought your site from page 2 to 1 in the serps. Etc.
Again i know it all requires a lot of work but iam interested in what add option perhaps drove your expectations over the edge.

Now that you mention it, I have received a peak of hundreds of new visitors when my main web site was reviewed on a big newsletter for webmasters. But of course it was only a temporary peak.