If you are creating your own import spreadsheet from scratch, or adding fields to the Import Templates we provide, here are a few guidelines.

In order for an import to succeed, a few conditions must be met:

Column headers in your spreadsheet must exactly match the fields where you are importing your information. For example: the Customer table has a field called "Phone". If the column header for phone numbers in your spreadsheet is called "Number" or "Telephone", the import will not work and you’ll be asked to correct the error.
You must have values for any fields that are required by your destination table. For example: in the Customer table, "FullName" is a required field. If one of your records does not have a value under that column header in your spreadsheet, the import will not work and you’ll be asked to correct the error.
You must ensure that any fields marked unique contain unique values. For example: in the Customer table, the "Name" field (first name + last name) must be unique. If you have more than one record with the same full name (e.g. two customers called Bob Crenshaw), the import will not work and you’ll be asked to correct the error.

It’s very important to verify your fields before proceeding with the import.

There are a variety of ways you can verify this information, but the easiest way for a new user to verify their fields is the following.

Verify Destination Fields are Spelled Correctly

The best way to make sure the fields are correct is to look at the table itself and compare the fields straight from there.

Click the profile icon in the upper right and select Account Settings
Click Tables & Fields.
Locate the table you want to import into (e.g. the Customer table). You can search using the search tool.
Click on the table to bring up a list of available fields in that table.
Cross-check the column headers in your spreadsheet with the fields in this table. Ensure each header exactly matches the field it’s intended to populate (e.g. ensure the column header for a lead’s email reads Email and not E-mail or email.)
When you are sure the column headers match the destination fields, click the Back button on the screen to exit.

Verify Required Fields

You need to view the Tables in Method so follow steps 1-3 above.
On the Field screen, you'll see a exclamation icon next to certain fields. This means the field is required for Method to save the record. Scroll down and make note of any fields with exclamation marks! Note: Stock tables in Method generally have at least one required field.
On your spreadsheet, ensure that the column headers matching required fields in the table have values associated with them (e.g. if Name is a required field, make sure each record you want to import has a Name associated with it in the spreadsheet).
When you are sure your spreadsheet is up-to-date, click the Back button on the screen to exit the table you are viewing.

View the Tables in Method as outlined in previous sections.
On the Field screen, you'll see a fingerprint icon next to certain fields. This means the field is Unique (require a unique value). Scroll down and make note of these unique fields.
On your spreadsheet, ensure that the column headers matching unique fields have unique values associated with them (e.g. if FullName is a unique field, make sure you do not have duplicates. If you do, you can append a duplicate with [1], [2], etc.)
When you are sure your spreadsheet is up-to-date, click the Back button on the screen to exit the table you are viewing.