Assets = Money you have. Liabilities = Money you borrowed from someone else. Equity = Money you earned.
All the money you have you either (i) borrowed from someone else or (ii) earned. In other words:
Assets (money you have) = Liabilities (money you borrowed) + Equity (money you earned).
When recording a transaction all you have to do is ask yourself two questions:
1. Where did the money come from? (what is the Source) 2. Where did the money go? (what is the Use)
Suppose you borrow $100 from a bank:
1. Where did the money come from? -> you borrowed it from someone else, so increase Liabilities by $100. 2. Where did the money go? -> to your checking account (money you have), so increase Assets by $100.
Adjustments to Source accounts (where money comes from) are Credits, adjustments to Use accounts (where money goes) are Debits, so we could revise the above statement to:
1. Credit Liabilities $100 2. Debit Assets $100
That's basically it. The rest is just breaking things down into sub accounts (e.g. Assets:Checking or Equity:Income).
Hope that helps.