What are common ways for contemporary Christians to fast? Which ingredients are being left out? (Besides meat, maybe spices? How about salt?) Are there different fasting dishes / cooking approaches in the various denominations?
In Orthodox Christianity, fasting is vegan (no meat, no dairy, no egg, basically nothing of animal origin). And no alcohol (that means avoiding vinegar, as well).

Monks and nuns (and some of the more fervent Christians) do it the proper, old way - vegan and without using oil (like olive or sunflower oil, for example).

Another aspect to take in consideration is avoiding a lot of food - one can fall in gluttony with vegan food as well, and that's not fasting anymore.

But more important than the food fasting is the fasting for the soul:


don't eat human flesh (don't argue with people, don't think bad of people, don't judge people, forgive everyone, be merciful towards everyone)
fasting with our eyes (turn your head the other way when you see an attractive person)
fasting with our legs (avoid going to sinful places, where we know we can fall)
fast with your mind (keep your mind in continuous prayer; in Orthodoxy, this is done with the Jesus Prayer - "Lord Jesus Christ Son of God, have mercy on me a sinner", said without interruption in the mind)
more prayer than usual, more meditation on the sufferings of our Lord
meditate on the Final Judgement questions (Matthew 25:31-46) - how do we help the ones in need? There are a few billions of people out there without food, water, shelter etc