Most Helpful Guy
Whether your talking to a guy or a girl, conversation will often go nowhere if one person isn't trying. That said, the easiest way to get a conversation flowing is ask them something about themselves. Especially in text, if you make a statement without giving them an opening, conversation gets kinda hard. If you get them talking about themselves, it's much easier. Instead of "oh today I went and did ___", try adding a question of them at the end.
Assuming your reasonably familiar with each other, e. g. you've known each other more than a couple months, try sending them a funny picture of something you both like. Ask them advice on something, even if you don't need it. If you recently had some kind of interaction with someone they know/sports team/family, open with that ("oh hey I ran into ___, they're your friend aren't they?""howd you get to meet them anyway?").
Key thing is ask them questions and be ok with NOT talking about yourself for enough time that conversation flows.