The best marketing strategy you can develop is one that uses multiple channels. Multichannel marketing gives you a huge advantage. When your message shows up in more places, it's going to be seen by more people. Not everyone responds to the same media either. Even if someone sees your Facebook ad, they may not notice your message until they see your direct mail piece or TV spot. No customer is everywhere at once, but when your marketing message is, your customer is bound to see it, where ever they are.
This is the main element of multichannel marketing - Variety. When you use a variety of channels, the chance of reaching your customer at the right place and the right time increases dramatically. But variety isn't the only element of multichannel marketing. There are two other things you have to consider when you develop your marketing strategy - Frequency and Consistency.
Frequency is a bit of a no-brainer. You have to put your message in front of your audience often enough that they will notice it, read it, and take action. The key is finding the right frequency. Too often and the customer will become frustrated with you, especially if you're spamming their inbox or mailbox. Not often enough and they'll forget about you all together.
The other side of the coin is consistency. You have to be consistent with your message and your frequency. If your message is consistent across each channel, the customer will remember it more easily and the heart of what you're trying to convey won't get confused or jumbled. When the frequency of your message is consistent, the customer will come to expect it and will be more likely to notice it. If you sent 3 emails to customers one week and then none for a month, it would either confuse or annoy them and make you look unprofessional, which would do more harm than good.
There is one thing that I didn't mention that you have to keep in mind for all of this to work, and that's to keep it relevant. Even if you send your message at a consistent frequency through a variety of channels, if your message is not relevant to your customer, they won't listen. If it doesn't speak directly to them, they will delete the email, ignore the Facebook post, and toss the postcard. Relevance is the most important part of any marketing outreach. If you can remember that, along with these other key elements, you will be on your way to creating a successful multichannel marketing campaign.