Soicial media, article submission and Guest Posting best Activities in Off Page SEO..

i agree, these are all great tips!

Off-Page SEO Strategies to Build Your Online Reputation.

1). Community Creation in Social Networking Sites
2). Blogging.
3). Forum Postings.
4). Search Engine Submission.
5). Directory Submission
6). Social Bookmarking
7). Link Baiting
8). Cross-Linking
9). Photo Sharing
10). Video Promotions
11). Business Reviews.
12). Local Listings & Yellow Pages
13). Article Submission
14). Press Release Promotion
15). Classifieds Submission
16). Social Shopping Network
17). Answers.
18). Document Sharing
19). CSS, W3C & RSS Directories Submission
20). Widget / Gadget Development
21). PPC Ad Campaign
22). Link Exchange

Lots of people are now using social media as an avenue to increase value of their website which is a very helpful technique.

Blogging, forum postings, photo sharing, video promotions, cross linking etc are some of the off page seo activities.

i think writing for your best keywords is the best strategy