What about doing a quick simple Mirror Test?

Stand in front of and facing a full length mirror and check the following:

1. Are your shoulders level?
2. Is your head straight and looking ahead?
3. Are the spaces between your arms (at elbow level) and sides equal?
4. Are your hips level, your kneecaps facing straight ahead, and your ankles straight – from a side view?

The following will be made much easier and give you a more accurate assessment with the help of a third party, or by them taking photos:

1. Is your head erect and not slumping forward or backwards?
2. Is your chin parallel to the floor and not tilting up or down?
3. Are your shoulders in line with your ears and not drooping forward or hanging back?
4. Is your stomach flat?
5. Are your knees straight, but not locked?
6. Can you see a slight inward and forward curve in your lower back?