Is it best to call ahead or stop by with a portfolio and try to schedule a meeting, or more of a shock and awe tactic
Im sure you'll will find many diff approaches but overall your main goal, once you contact, is to always be accessible, friendly and build relationships.
Even if your relationships are thin, they are better quality leads for business than you simply walking into a business pitching your product.
When pitching your product:
Always focus in value, talk to your soon to be clients as if you deal with the issues first hand and this is how you solve them... Don't discuss pricing unless asked. Offer any help or guidance in selecting services even from the competition if they want.. Sell yourself as a rep from a company that is paid to help not sell...
This approach works wonders if you can pull it off..
If you have less time during intros or pitching local retail shops you have to be more direct but still aim for a relationship than a quick sale before you move on next door. Learn a bit about their business like busiest hours, popular item or service...after your intro simply offer them more time when they are less busy with clientele to come back to talk about fuckng a certain issue (with a product you represent) :)
Hope it helps a bit.
Don't be a salesman at all. Go in with a genuine interest of helping these people. Ask questions and give advice intertwining your product. When you go in with the attitude of really trying to get to know about their issues and giving advice of what they can do, this changes everything and people are willing to open up and talk. Works like a charm.