1. Product Page Upsell
2. In-cart Upsell
3. Post-Purchase Sequence
A Thread on How To Implement Them:
The key is to really play up the urgency. Slash the price by 30% and state this is a one time only offer
I'd say 1/10 is standard for the upsell. But, if you make the offer relevant it can be closer to 1/5
"Add X for only $14.99? (normally $25)" will work perfectly. This will convert better than the upsell up, especially if the add-on will qualify them for free shipping
Send out an email immediately. Thank them. Introduce your brand story. Tell them their order will be shipping soon. Then give them a 25-30% coupon.
Make the coupon unique, so it's believable. Something like "25Off-DmT"
Then 2 days later send them the last email that says the code is expiring in less than 24 hours. My first post-purchase does okay, but the second one converts like crazy. All this can be done in Mail Chimp