I am often asked what is the best way to make sure you have set-up the Marketo profile correctly for the Marketo SFDC login user. Here is the process I use to verify the set-up and get an accurate count of the records which may be syncing.
Step 1 - Have your SFDC Admin double check that Lead Custom Field Mapping has been completed correctly.
Step 2 - Make sure the Marketo profile can create SFDC reports.
Step 3 - Login to SFDC using the Marketo User for SFDC. Make sure you are logged in as the Marketo SFDC User and not as an Admin or though your own login.
Step 4 - Navigate to the SFDC Reports Tab and create a New Report. Run reports for Accounts, Contacts, Leads, Campaigns, Opportunities, and Tasks and Events.
Step 5 - Spot check each report for fields you should not see and note them down for your SFDC admin to fix the Marketo profile.
Step 6 - After you look the fields, write down the counts for each report. Make sure the filters in the report are showing all records for all time. If you are planning to use a Marketo custom sync rule run the counts with and without this filter. If you see a dramatically different number than you were expecting then work with your SFDC admin to review any permissions or sharing rules in place.
Understanding the counts will also give you a rough estimate of how long the initial data sync will take. Divide your total number (Accounts, Contacts, Unconverted Leads, Campaigns, Opportunities, and Tasks and Events.) by 15K/hour to determine how many hours it will take. The initial sync speed is fastest during the evening and on weekends.
If you have millions of Tasks and Events and don't plan to use Tasks in Marketo you can ask Marketo Support to disable the syncing of Tasks and events.
Step 7 - Try editing a test contact and lead and saving your edits. It is helpful to document any validation rules you might see so when you are using the Change Data Value flow step in Marketo you can remember to set the values of fields correctly to avoid validation sync errors.
Step 8 - Ask your SFDC admin to make any necessary corrections to the Marketo profile
Repeat Step 5 if necessary.
Congratulations, you are now all set for a successful SFDC sync.
Additional resources for learning about the Marketo integration with SFDC.