Temperature: You should never blend or fix mortar when the temperature is at or below cold.
Bagged mixes: If you need peace working with blend ratios, use bagged concrete ideally. All the elements have already been calculated in the exact quantity and blended for you.
Mixing by hand vs. equipment: Using a strong blend gives a much more compatible blend. Mixing little batches by hand is excellent, but a powered blender is much better, especially for big projects.
Water: Getting the proper water level is optional when working with concrete. Both too much and too little water will weaken the mortal and cause it to the wrong failure.