Bear in mind the other factors that effect the value of a backlink:
relevance to your sites subject matter is helpful.
link sources where you can set the anchor text to your keyword phrase.
of course dofollow links are essential for search ranking, spamming Yahoo Answers doesn’t help one’s search engine ranking.
References :

Nevertheless, should your website or opening webpage
fail to contain "generic" keywords, then anyone using
such "generic" queries will not be able to discover
your website. Your domain name [URL] of your website,
in a sense, will be invisible, undiscoverable.

You may want to consider some simple algorithms which,
when observed and committed in designing of a website
with placement of various critical metatags that can
surely achieve a high search engine presence and
increase Internet traffic to your website. These
metatag strategies work well with published webpages
at Google and Yahoo.

Design: Should you create an extensive Flash-based
website, make sure to fill-in the property entries
such as the Title, Description and Keywords. Failing
to do so, leaves no hard HTML or ALT resource that can
be readily indexed by search robots. Also consider the
Internet audience and their incoming setup. For
example, if they are on analog/dialup, Flash webpages
take too long to load up and therefore analog users
will likely lose interest and discontinue entering the
Flash site. On the other hand, anyone on hi-speed DSL
lines, will welcome Flash pages which load quickly. So
before designing a pure Flash websitge, ask the simple
question, "Who’s my end user – is he on dialup or
DSL?" And if you had to choose between these two users
for maximum marketability, then select analog users
since 80% of most resident users are still analog
Internet subscribers and pure HTML designed webpages
is best for them.

A non-Flash-based website which relies on hard text,
is far easier to be indexed by search robots. Limit
the use of stylized text saved as .gifs since as a
graphic, they are not indexable by search robots.

Avoid use of frames since any number of search robots
are unable to properly classify textual material.

Placement of Metatags:

A ranking or search order does take place with Google
and Yahoo and it begins with the "Title" metag which
should consist of no more than 65 characters separated
by commas. The "Title" should describe in generic
terms, the goods and services, followed by a location
from which the resource is located, i.e., city, state.
The placement of a domain name which is not generic
within the "Title" is not appropriate, unless your
domain name is a major recognizable brand name.

The second metatag is the "Description" which is
usually 25-30 words to form a complete sentence which
best describes one’s goods and services.

And the very last category – "Keywords" are also
somewhat limited to 15-16 words which can be plural
and compound in nature. Again, avoid multiple entries
which could be mistaken as "spamdexed entries" which
is defined as the loading, and submission of
repetitive words into a particular metatag category.
"Spamdexing" when discovered on a webpage and reported
to Google’s spamreport.com can result in the
elimination of your website from their search
directory.

Good luck!
References :
Based on an seo webmaster article from google.com.

There are lots of ways of doing that you can do directory submission, article submission, blog commenting etc…

You can get help of professionals too, we have been using Internet Search Optimizer for our website… i suggest you other company because building back links is continuous and tedious work..

You can contact them at http://www.internetsearchoptimizer.in or email at info@internetsearchoptimizer.in
References :
http://www.internetsearchoptimizer.in

Yahoo needs a Yahoo Id but its free.
References :
http://backlinkwatch.com/index.php
https://siteexplorer.search.yahoo.com/mysites

Socially bookmark all your pages of your site, that will help with indexing.
References :