Measure rice and urad dal, usually in a 3:1 ratio.
3 Cup Rice, 1 Cup Urad Dal
Rinse and soak them, each in their own bowl, for 6 hours or overnight.
If you are using fenugreek seeds, soak and add in the urad dal bowl.
1 teaspoon Fenugreek Seeds
If you want, toss in a teaspoon of fenugreek seeds to soak with the dal.
Once the dal and rice are soaked, and ready to grind, discard the water.
Rinse again and grind to a smooth paste using minimum batter.
Do not make the water too much runny.
More tips and tricks on batter can be found in this post on how to make and Ferment Idli Batter.
Add Salt and mix.
Salt as required
Cover and Let the batter ferment for 10-12 hours or overnight. More time might be required in cold climate.