The stories in the front page are sorted by "penalties * upvotes / time^1.5" (Where penalties are a lot of automatic an manual penalties added by the mods and the flags of the users.) (And the number 1.5 is only an approximation. I don't know the current value of "gravity".)
Using this calculation, to get to the front page, post currently must get 3 or 4 upvotes in the first hour.
There is also the second chance pool, that sends a story to the front page for a short time. More details in https://news.ycombinator.com/item?id=11662380 The mods use a mix of manual and automated criteria to add stories to this pool.
The details change from time to time and are part of the secret sauce, so take this as a rough approximation.
And remember to go to the newest page and upvote good stories https://news.ycombinator.com/newest