Bring a large pot of water to a boil and salt it (or you can steam the greens over an inch or so of boiling water).  Cook the greens until tender.  Drain well, then place in a covered bowl and refrigerate (for up to two days).  Or cool by plunging them into ice water or running under cool water.
Squeeze excess moisture from the greens, then chop them coarsely.  Toss with olive oil, lemon juice, salt and pepper, then taste and add more of anything if necessary.  Serve immediately.