When considering which custom fields you need to add to a process, it is helpful to know what LeadSimple already tracks by default.
Leads - These fields are included in the details section on leads inside of pipelines (Owner leads, Appfolio Owners, Appfolio Tenants, etc). Note that these fields will not be available as merge tags in Processes, only in Pipelines.
Contract Start Date (on closed leads)
Contract End Date (on closed leads)
Closed At (on closed leads)
Properties - These fields are included on the Property card and will be available anywhere that property card is used (pipelines or processes).
Address line 1
Address line 2
Units (Single family properties have one unit, multi-unit properties each have multiple units) - These fields are also on the Property card and will be available anywhere that property card is used. If a property has multiple units, each unit can have it's own value in these fields.
Lease Start Date
Lease End Date
Contacts - These fields are included on the Contact card and will be available anywhere that Contact card is used (pipelines or processes).
Processes - These fields are included in the details section on processes inside of process types (Lease Renewals, Move Outs, Marketing, etc). Note that these fields will not be available as merge tags in Pipelines, only in Processes.
Now, if your custom field isn't on this list, you will want to add it. (Help article linked here.) Note that you will have to decide where to put your new custom field in LeadSimple as custom fields can only be added to one of the above categories (Lead Details, Property, Unit, Contact, or Process Details.)
Here's a quick rule of thumb when decided which category to place a field into:
Will the value of this field always be the same (ie. HOA - Yes or No, or Pets allowed? - Yes or No)? Will this value, once selected, need to carry to other processes? If so, place it on the property, unit, or contact as applicable.
Will the value of this field possibly/likely change every time we run this process? (ie. Tenant Renewing? in the Lease Renewal process). If so, place it in the Process Details and not on the property as it will need to edited every time we run a lease renewal on this property.