Company:
For starters make sure you go with a company that has dependable servers that you can offer to your hosting clients and potential clients. Make sure you are able to have a support system inwhich your clients are able to contact you within a short amount of time whether it be a support number, email address or trouble ticket solution. If you provide great service your company will eventually spread like wildfire. Word of mouth is powerful in this industry and people are fed up with hosts that don't provide the service that they are paying for.
Marketing:
Make sure you have some sort of marketing budget that you spend every month. You need as much exposure to your hosting brand as possible. Advertise locally and on the internet. In the local market walk into small business shops (storefronts) and let them know who you are and what kind of service you can offer them. Most importantly explain to them how they could benefit from having a website online. If you have the budget to do so get some professional information packets printed for your company that you can give to people. Find a list of businesses addresses in your area and mail them out. Internet wise you are appealing to the global market. You have to be smart about how you advertise online. For each sale that you get make sure to come up with some sort of percentage basis on how much you would like to put back into advertising your company. If a new customer is paying $30.00 a month for hosting and you are profiting from $10 of those dollars take around 60% of that profit and recycle it back into advertising on google adwords or purchasing backlinks to your site. Definitely make sure to post often on forums and make sure they you have your hosting company website listed in your signature!
Hope this helps a little!