“A mnemonic device is a mind memory and/or learning aid. Mnemonics rely on associations between easy-to-remember constructs which can be related back to the data that is to be remembered.” Wikipedia.
These are the mnemonics and heuristics I use the most:
RCRCRC
Regression Testing Heuristics by Karen N. Johnson
Recent, Core, Risk, Configuration, Repaired, Chronic
SFDIPOT (San Francisco Depot)
Test Strategy Heuristics by James Bach and Michael Bolton
Structure, Function, Data, Integrations, Platform, Operations, Time
CRUSSPIC STMPL Quality Characteristics Heuristics by James Bach
Capability, Reliability, Usability, Security, Scalability, Performance, Installability, Compatibility, Supportability, Testability, Maintainability, Portability, Localizability
A variation to these heuristics can be found here. I like the added Charisma-heuristic http://thetesteye.com/blog/2010/11/software-quality-characteristics-1-0/
FEW HICCUPS
Test Oracles by Michael Bolton
Familiarity, Explainability, World, History, Image, Comparable Product, Claims, User Expectations, Product, Purpose, Standards and Statutes,
RIMGEA
Bug Advocacy Mnemonic by Cem Kaner
Replicate it, Isolate it, Maximize it, Generalize it, Externalize it, And Say it Clearly and Dispassionately
MOCHA
For asking questions in e.g an interview – by Maria Kedemo
Meta, Open, Closed, Hypothetical, Audit
Here are some more which you might find useful