"How's your day going?"
"Hey, I was wondering what your schedule was like for the next week?"
"Is there a good time this week to meet up?"
"I hope you're well. Wanna do something soon?"
"Hey, I was just thinking about you. Are you free anytime this week?"
"I haven't heard from you. Let me know if you are free at all to hang out."
"Just wanted to say hi. If you are around, let me know."