I only answer the phone if the call is from someone on my contact list.

My phone is in Do Not Disturb mode 100% of the time, with only alarms and priority calls whitelisted, so I know that if a call comes through, it's probably important.

Everyone else can send a message or record a voicemail. I'll call or write back when I feel like it. I have also taken the step of disabling all notifications except for direct messages to me. Those get to pop an icon in the notification bar, but no sound nor vibration alerts. I'll see the message whenever I decide to check my phone.