Great question! I do not really thing there is a straightforward answer for this - personally I tend to get an SEO agency working on the SEO side of things and then I push some social media campaigns / Google ads campaigns.
Web hosting forums are the best way of marketing web hosting services, but do not spam anything anywhere. Customers coming from forums are very intelligent, they know how to destroy your brand name on the internet by making bad comments on the forum, so present the product in original and do not present any false information about your product.
There are several ways you can promote your small business with the real and effective marketing strategy:
Setup your optimized Google my business listing page and fill out all the necessary business details.
Start submitting your business details to the high PR local business listing websites.
Start posting free ads on free classifieds ads posting websites.
Start sharing some real good images of your business to the top image sharing websites. You can find dozens of online free images creation/editing tools.
Start promoting your business via Facebook pages and run low budget page likes ads. You can easily get page likes from your target audience.
Start your business promotion via LinkedIn profile/business page. LinkedIn also provides $50 of free ad credit.
Run Google ads to showcase your business online via Google search results page. If you want more phone calls, you can setup call only ad campaigns which brings more phone calls through the mobile device users. Google also provides $100 worth of free ad credit.
Use other social media sites to promote your business.
Use content marketing strategies such as, setup your free blog on blogging sites like blogger, wordpress etc. and promote your business via posting articles about your business.