How do I make sure I don't land in the spam folder?

The biggest thing you can do to stay out of the spam folder is to work off an opt-in email list that you built yourself -- not one that's purchased or rented. You should also follow best practices like identifying who you are in your sender name, making unsubscription easy, segmenting your lists and tailoring your content to those segments, cleansing your lists, and not bombarding your recipients' inboxes with too much email.