what would be the best practise for connecting mailchimp with Salesforce?

Here is step by step process for Salesforce MailChimp integration through an app.

Firstly, install and configure the app in Salesforce. The app is quickly available at the Salesforce AppExchange for download.

Once you have installed the app successfully, the next step is to define MailChimp sections to your content layouts. For this purpose, go to the Setup -> leads/Contacts -> Fields -> Layouts.

In the Layout, you can see the VisualForce page. Simply drag and drop the Membership Contact section to the layout created by the MailChimp app you installed currently.

For professional or unlimited editions, you can also add MC fields in the layout designer section. You have the flexibility to change the fields in the Layout Designer section.

Don’t forget to save the changes at each step.

Reference - https://www.janbask.com/blog/mailchimp-and-salesforce-integration/

Hey Dharani,
The best practice for connecting MailChimp with Salesforce is through third-party applications. An application that I would like to personally recommend is ChimpConnect. You can know more about this application here:
https://eshopsync.com/mailchimp-salesforce-integration/
https://eshopsync.com/mailchimp

Hello Eiyu

The best way to integrate Salesforce and Mailchimp is through a third party application.

Step 1 – Install and configure app in Salesforce org. (Apps available in AppExchange)

Step 2 – Define MailChimp sections to content layout.

Step 3 – Drag and drop membership contact section through Visualforce page.

Step 4 – Add MC fields in case you have professional edition.

Step 5 – Save the changes

Personally, I would suggest you to take the help
from professional Salesforce consultant. For details on Salesforce Mailchimp
integration services, you can take help from here – https://www.fexle.com/salesforce-mailchimp-integration