My 99 Ranger's heater only gets lukewarm, on most days it's ok except in the early mornings and then it's not very comfy.
Any ideas?

 

Try flushing the heater core. You can easily search Youtube for a video if you aren't comfortable with doing it. It takes only a few minutes to complete.

 

Yes, Google: Back Flush Heater Core

Ford, chevy, toyota, etc............doesn't matter they are all the same method.
This should be done on every coolant change, so every 2 - 3 years.


Rangers have had issues with the Blend Door, this is inside the cab and allows the heat from the core into the vents.
Google: Ranger Blend door