One of the main goals of your website should be to ask visitors to subscribe to your email list. At what point during their visit should you ask them to subscribe?
Asking on the Homepage
Having a subscribe form on the homepage can come across as being too forward. You wouldn't walk into a bar and ask a girl for her phone number right away. Instead you try and start a conversation before you ask for personal information. For tasting room traffic you wouldn't ask a visitor as soon as they walked through the door. Here again you try and start a conversation before asking for their email address.
Asking visitors to subscribe on your homepage before they have had a chance to learn about your company and your products will result in fewer subscriptions.
Asking during Checkout
A second alternative is to ask a website visitor to "subscribe" during the checkout process. This is really important however you will only be collecting email addresses from your purchasers and not from your non-purchasing visitors. People who never go through the checkout process will be missing out.
Asking based on Location
Where is the correct location for a subscribe form?
It’s my opinion that you should ask for a visitors to subscribe around the 3rd or 4th page they view. At this point the website visitor has shown some interest in your website and your products. You should also have the subscribe option show up in key areas of the site such as the 'About Us' page and if there is room on the navigation, having a 'Newsletter' or 'Email Offers' option. (Ideally this subscribe form should only appear if the person visiting the site isn't a subscriber already.)
Email subscription forms can be stand alone elements or built right into the website copy (for example, on a product page, you can ask people to subscribe to learn about new product releases and when next year's vintage of this wine will be available)
Email subscriptions should be one of the main goals of your website, and therefore both the copy and the form placement should be tested for optimal conversion rates.
In the offline world, you should have a subscribe signup sheet right at the tasting room. This is one of the easiest ways to grow your email subscriber list. (You can then take this hand written list, manually insert them into your subscriber database, and with the right tools have an email generated to each subscriber thanking them for visiting your tasting room, introduce your website, and asking them to "opt in" to your email list)