What leads to sync between MKTO and SFDC?

I think almost everyone syncs everything. It's totally okay to do, but is also highly dependent on your lead assignment rules/the way your business uses SFDC and Marketo. I tend to keep the Marketo profile in SFDC the owner until they reach their scoring threshold, then they're assigned through the SFDC rules.

However, if you're not able to do this, your reps will see leads before they are ready/have reached their threshold unless you're using predictive lead scoring. If you have a sales team that doesn't jump the gun/doesn't hunt for leads in SFDC, then it's probably okay to sync everything. If not, you may want to hold them in Marketo until they've reached their MQL stage, then sync them into Salesforce. The flow for this would be "Trigger: revenue stage is changed, new stage is MQL" then "sync to SFDC" in the flow. Using the modeler makes lead routing/holding things back in Marketo markedly easier than without using it. 

Currently I sync everything, but the issue is storage overages. I need to decide what leads are necessary to keep in Marketo, and which are fine to leave in SFDC without syncing to MKTO. 

We currently sync all leads. We have some issues with SFDC assignment rules and routing currently but are working through it :)

I'd start by deleting leads in Marketo that have bounced email addresses and working to delete dupes. All leads that don't have an email address in Marketo but exist in SFDC are the other set of leads I'd delete since they're taking up space and you're not able to email them. You can pull smart lists of all of these and see what number that comes out to and if it would make an impact on freeing up some space. 

Other than that, I'd keep everyone else. I hope that helps a little!

I agree that all leads shouldbe fully synced. You can hold back non MQLs in a Lead Queue if that works with your process. Then trigger the LARs with a status change that's in apex code. (Kim P).

I would be surprised that you have storage issues in SFDC. Are you syncing all activities? If so, stop that, then you will have plenty of space.

It makes life harder eventually to hold leads in Marketo only and then sync them later. Lots of duplicates can occur.

Hey Josh! Our SFDC admin is not sure how to do that and is very reluctant to look into anything for our marketing dept. Could you tell me how complex this particular coding is and about how much time it typically takes? Thanks!

Our storage issues are in Marketo, so we are trying to alleviate by only syncing necessary leads from SFDC to MKTO. THoughts?

We sync everything, but I'm finding leads in Marketo without email addresses. They have a SFDC Lead ID, but no email.

What is the best practice?
Is there a way to filter to prevent leads without emails coming over?