What are the best "standard" Marketo feilds to sync to our CRM?

Here is a great start: https://community.marketo.com/MarketoTutorial?id=kA250000000Kz5rCAC
Follow all 4 steps. 

After syncing those fields, you would sync any other fields that you want Marketo to see and use (for both standard and custom fields). These could be for forms, smart lists, etc. in Marketo. 

I would be very careful with privacy information fields. They do not need to be in Marketo. 

Hope that helps!

Chad,

If you have a complex SFDC, then you do need to consider which fields to sync. If you have a more standard, out of the box setup, then just sync it all.

Key fields:

• contact information
• campaign data
• subscription/privacy fields
• customer identification - who is a customer? how do you know?
• Status fields
• Source fields

DO NOT EVER sync a field with SSN or Credit Card or passwords. Marketo is not PCI compliant and it would be far too easy to prefill a form with this detail. I had a client who did that once and we had to clear out the fields after breaking the sync.

I disagree with Sydney - subscription/privacy fields MUST be synced to Marketo to build the Subscription Management Center and ensure you adhere to privacy and communication laws globally.

Josh,

The sensitive private information fields ARE these ones: SSN or Credit Card or passwords...
They should not be synced. 

This has nothing to do with subscriptions. I think you misundertsood. It's ok.

Privacy information is not always the same as sensitive personal identification data.