Hi Awalters,
A Contact can be a donor, a volunteer, a sponsor contact, a board member, a committee member, a member, even an individual sponsor or have other roles with your organisation.
An Account may be a donor, a volunteer provider, a sponsor, a supplier, a programme partner. An account could represent a business, a corporate, another charitable organisation, a community group, a government organisation, a school or even a household. (You could have an Account Type field that allowed you to categorise these.)
This information is best all stored on fields on the OOTB Contact and OOTB Account records. (Holding this categorisation data on the Contact and Account records means that it is easily available for campaigns and reporting.)
Then those Contacts and people associated with Accounts interact with you - send you emails, you might meet with them (appointment), you may send them a letter - that is what Activities are for.
* I have set up a Custom Activity type called Volunteering Activity for some charities, that allows them to track who has made what time commitment to their organisation. This can be useful for statistical reporting regarding level of community involvement.
What you set custom entities for are the parcels of things you want to track/group (each of these can be linked to a primary Contact, possibly a secondary Contact and/or an Account e.g. 1 Contact:N Annual Memberships, 1 Account: NSponsorships):
* Annual Membership (if you need to track some form of formal paid-up membership)
* An Event (which you might consider using OOTB Campaign for - Event is one of the categories of a Campaign)
* A Commitment to make a Regular Donation (which might have a 1:N relationship to the Financial transaction)
* A Sponsorship (which might have a 1:N relationship to the Financial transaction)
* A Programme - something your organisation delivers into your target community(which could have relationship links to campaigns, sponsorships, events, financial transactions etc)
* A Financial Transaction (which could have a category of Donation, Regular Donation, Sponsorship Invoice, Product Sale, Membership Dues etc), which you might consider using the OOTB Invoice entity for)
You might use the OOTB Opportunities to capture,organise and manage fundraising opportunities (and even volunteering applications).
You might use the OOTB Cases to manage brand abuse, public complaints, feedback, suggestions, advocacy topics etc.