Following points are a must to do for On-Page optimization:
Title Tag-> It should be descriptive that which services do you provide?
Keywords-> You should target such keywords whose monthly searches are high along with keeping competition factor low, if possible.
Meta Description-> Make full use of 165 characters, which Google has allowed you. Make it descriptive in such a way that’ll attract your customers. Mention the services you provide.
Alt Tags-> Alt tags should be placed in a right manner, but make sure that none of the images are missing alt tags.
Sitemap.XML-> Your website should have its sitemap as well. Provide one as it’ll be helpful for your site.
The list of Off-Page optimization factors is quite long but I’ll mention the ones which you should try as a beginner. They are listed below:
Social Bookmarking
Ping
Social Media Profiles (Twitter, Facebook, Google+, LinkedIn, Pinterest etc.)
Local Business Listings
Blog Posting
Article Posting
Directory Submission
Forums Posting
Answering Forums (Quora, Yahoo etc.)
Classified Ads
Keywords Research
Back links Analysis
I hope my answer will be helpful to you.