Like the other said, you want to make it a lot more personal than a simple "new number" text. Use his name or something so he knows you're talking to him and only him. No one replies to mass texts.
Furthermore you probably want to have a point to the conversation. Otherwise it'll dry up in small talk and one of you'll get bored or run out of topics. While a "how are you" might start a conversation, you need to get off that basic stuff asap.
Hell if you're feeling adventurous try texting to try and meet up or something. Any flirting etc can be built around that too so you'll have some indication of whether he's interested in you as well.
There's something I was recently taught: In early stage relationships you want to text for one of two reasons. Either you want to build rapport with the reciever, or you want to ask them out.
No idea how truthful that is, but it sounds pretty good on paper.