Put yourself in girl's shoes. Random guy chats you up and talks about random stuff that you carry with you or that you own. It might be pleasant conversation but for you but when that topic is dying out and there's no reason to talk to him more you probably leave.
The best way to get anyone's attention is to talk about stuff directly relevant to that person. What's the #1 thing people care about? Themselves. That's why it's best to make conversation personal. The quicker the better. You can start talking about whatever to break the ice but do not carry on that random topic. Switch from "stuff" to her.
Have you ever noticed that beautiful spontaneous smile girls make when they realize that there is romantic interest behind your conversation? That's the moment where polite chit chat stops and real interaction starts. That's when flirting starts. That's when your intentions are known. You want it to happen fast. You can make that switch smooth or messy, it's your choice. So whatever you do please don't ramble about stuff to drop some kind of bait hoping she will bite.
Example:
A girl with white laptop. So you want to use her laptop to start conversation. Good for you. You ask about the laptop. She talks back. To switch smoothly from that boring laptop stuff you can ask her why she chose white one. then you can tell her that you read recently that American scientists discovered and proved that women who choose white equipment over black actually want to get married quickly and they pick white cause they subconsciously associate that color with wedding dress blablabla.. then you can ask her if her boyfriend proposed to her.. then you can ask her if she's good wife material.. then you can ask if she can cook.. etc.. and now the convo is alive and flirty and about her exclusively. [keep in mind that you have to be really persistent and believe your bullshit cause girls usually disagree and try to discredit things you say especially when what you say is edgy or make them look bad/ridiculous haha]
This way you're leading instead of hoping/waiting and you can convey your sexual interest in fun creative way instead of playing chess. Now she might reject you of course but as long as you transition fast she won't leave or ignore you.
To practice you can think of things girls carry on or situations where you meet girls and think about how to use that stuff/scenarios to express your interest.
Very relevant:
/thread-31002-...#pid609679
/thread-27791-...#pid529270 [cool indirect section]