I started off, recently, in S5. After a losing streak, I ended up in BII and haven't tried to climb out. My advice, because you can't control who you are paired up with, is to accept that streaks exist. Don't push it if you aren't winning as you're just going to continue losing points. Make sure you're wining a few games in norms before you attempt to grind out of bronze. Let me know how it goes.
When season starts, just play well. Focus on getting cs and not dying. Your starting rank will be weighted on your individual score, even if you lost a majority of your first 10 games.
In addition, it probably depends on how you play your champs. As I usually concentrate on just a handful of characters, I'm most often playing something that I have a M7 or M6. As a result, I'm usually playing with other M6/7s. If you're all over the board with 10+ champs, its harder to get good quality games. It also takes a lot longer for the good games to get started again than you may realize. I'm not sure if/how this applies to ranked specifically, but for normal mode its mos def a thing.