You can use any format as long as it contains the following:
- Expected Result
- Actual Result
- Pass/Fail Mark
Other organization also prefer putting a traceability column which traces test case back to the requirement specification.
As for how to make test cases, different organization uses different techniques, one technique that I find interesting is the Test Agent Model (JAVA Testing and Design Book). As for some organization they start would first with a Test Design Specification before jumping into Test Script Specification writing.
Test cases should be consisting of the following:
OBJECTIVE:High level description of what u intend to test through the script.
PRE_CONDITION:Some assumptions,i.e., assuming certail criteria are already met to start running the script.
PASS CRITERIA:When will the script will be success.
DESCRIPTION: Details description of the script
TEST DATA: Data required to test the pass criteria.