1st step: make sure all your pages are optimized – specific keywords, keyword density (around 8%), different title tags;
2nd step: make sure your internal linking structure passes importance to where you want it;
3rd step: get links! And where you have control, ensure the anchor text matches the on-page keywords/content.
Steps 1 and 2 will take you very little time – they should be built into your site design process.
Step 3 is ongoing and infinite. Getting natural links takes time. If you’re tempted to go down shady routes, you’ll buy short term success and long term ruin. Give it 12 – 18 months mimimum before you expect too much return on your work.
Best advice: Do the right things and be patient!