How to make my Avid Elixir 1 hydraulic brakes more firm?
This can be down to a misaligned caliper.  Ideally when you apply the brake both brake pads should hit the rotor at the same time.  If you can see a visible deflection in the rotor when the brake is applied then you need to adjust the caliper position.  The loosen it off and apply the brake method rarely works for me, I get much better results lining everything up by eye.  Also remember the caliper will try and move as you tighten the bolts up!
If you still have a squishy feel when the caliper is aligned then a bleed is the next thing to try.