Start with knowing your email marketing provider. Always check the "tools" button and then decide how you will use these tools. Don't just accept the general settings. Be personal and remain professional. The next step is knowing when to send that email blast. Don't send one on Monday morning and never send one between 8 and 10 am. The best time of day is in the afternoon, not just as people arrive to work.
In closing, use what works and what will promote your brand. If you see people are not responding to offers sent on Tuesdays at 4pm, try a different day and time. If they still are not responding- rethink the offer!
Keep checking-in here for more FREE business advice.