This is what I think...
When you're living together:
Unless work/school schedules just happen to prevent it, yes talk every day. There can be times when two people have jobs that have hours that make it impossible for them to see each other, or they only see each other for fifteen minutes (and one of them is sleeping for that time). Life happens. But if everything is otherwise standard, a couple should talk about just almost anything every day, even if they aren't always interested in what the other is saying.
When you're living apart:
Connecting on the phone (preferably voice in addition to text) daily is important. There should be a date night every weekend and a couple lunch dates throughout the week, if schedules permit. More days should be spent together with conversation about your families, childhoods, past experiences, etc. You can start to lean on them if you've had a horrible day now and they'll be prepared to console you (and vice versa).
If you've just started dating and aren't officially serious:
Every few days there should be a phone call, a text, an email or something to say, "Hey, I'm still alive. You too?" with a standard weekend date night and maybe a lunch date every other week, if schedules permit. Conversations should be light and about interests, things you have in common, and ask questions about them (and listen to the answers). Funny and happy stuff is better.