The best conversion rate usually comes from being super-targeted with your promotions. Some examples are:
- using Facebook advertising to narrowing your criteria for your ad to appear
- on Google Adwords by selecting particular publications to advertise on
- approaching selected companies to collaborate with and run a joint promotion
This all hinges on how well you know and understand who you're marketing to. Any type of mass promotion generally has poorer conversation rates but can be a good starting point if you don't fully understand who your product or service best appeals to.
There is no simple answer for this question, aside from the fact of having a carefully constructed marketing plan which is relative to your budget which allows you to measure all of the data in and out of your business. It makes sense to monitor your campaigns, as you will see some will have higher ROI than others, yet some methods can be a seasonal glitch for example.
So I believe you should take close attention to where your customers are, what they do, and how to interact with them.
As @Jill Brennan mentioned, being super targetted is the key. But before you even start promoting your business, you need to be super targetted with who you are targetting!
You need to pin down who your target market is, get to know as much as you can about them, gender if applicable, age range if applicable, etc. We recommend that you fill out a persona template with these details. If yu do a Google search for persona templates you will find plenty but Hubspot has a great template you can download.
Once you have your target market sorted, now pick your perfect buyer from that group and narrow them down even more. If you already have an established business then ask yourself who are your absolute best customers, the ones that you would love twenty more of, then work out what they have in common and prepare a persona from them.
We recommend that you even go so far as to download an image of your perfect buyer from the net, and give them a descriptive name, like "Betty the harried housewife", or whatever. Pin the tersona template up on the wall where everyone in your business can see it.
Now, whenever you write anything for your business, from sales pages, to blog posts, to Facebook ads, all you need to do is to ask "What would Betty want to read?" and your copy will practically write itself. And your conversions will go through the roof, because you are targetting just one person, your perfect buyer!