Best way to get a .dev domain name before everyone else

There are no cheaty tricks in the case of .dev. The basic gist of it is that the more you pay, the closer you are to the front of the line.

Timeline: If you own a trademark, you can get a corresponding .dev domain starting Jan 16 2019 if you pre-register right now. If you don't have a trademark, you can get a desired domain starting Feb 19th for a likely very hefty fee. The fee decreases until Feb 28, at which point anybody can register a domain for the registrar's standard fee.

Source: get.dev

There is no "best" way, only heuristics.

.dev is a gTLD. It is run by Google, and as any gTLD it is covered by ICANN rules. Its startup information with dates can be seen on https://newgtlds.icann.org/en/program-status/sunrise-claims-periods/dev which is the authoritative source beside the registry itself.

All the above would apply exactly the same way for any TLD (at least gTLD), there is nothing specific to .DEV which has nothing specific in fact except

1. the semantic you may be willing to attach to it, and hence its value
2. the fact that technically it is loaded in the HSTS preload list, but this has only consequences for HTTPS access on websites in an .dev domain name, not registrations

Is there maybe a way to buy a domain the first second it's available?

You are targeting basically the landrush phase where almost no domains exist and people try to grab them. It is a little different from another case when people attempt to grab domain names that have expired and about to be back to the public, but the technical consequences are the same.

I am sure that you can imagine you are not the only one in that case and even maybe someone wants the exact same name as yours.

In case like that for high wanted names, you can be pretty sure that no manual process will win. Companies have automated robots that will send commands far faster than any humans. Some registrars may allow you to "pre"-register, by paying or not: you give them the domain you want and they will try to grab it, at the moment they can send the command.

Noone can guarantee you they will succeed, first because registries are mandated by ICANN to give equal treatments to all registrars (regarding number of connections, filtering, etc.) and then because a registrar may get two orders for one domain so, if they catch it at the registry, they obviously will need to disappoint one of their 2 customers. Or put the name in auction.

For all the above reasons, if you go the "pre"-registration route, make sure to read very closely the contract you are signing for this service.

ICANN and registries are mostly cautioning people not to enter into such schemes.

Besides that:

1. like any gTLD, there is a sunrise phase, so if you have a matching trademark that is registered on the TMDB then you can get the associated domain, for a specific fee. It happened in the past that people registered marks just to be able to register the domain name. But it would be too late for you as typically only trademarks existing before a specific date will be taken into account
2. after that, for the first few days, the registry decides to offer domain names at an higher price, which is lowered each day until becoming the standard registration price. Then it is a bargain you have to do yourself: you want example.dev, it may be sold at $1000 (fictional values) on day 1, $800 on day 2, $500 on day 3, $100 on day 4 and finally reaching on day 5 its normal price of $20 (I do not know, all values are fictional). Depending on how much you want to invest you can try registering it on day 1, or 2, or 3, etc. Of course someone having more money than you can register it before you.

Or can I get access some hours earlier by using a vpn into a specific country or registering it from a registrar in a specific country?

No, because like I said all registrars get same treatment from registry. Now, some may be smarter then others in the way they use their available connections and the way they send their commands, both in the order and content, but of course noone can predict who will win.

Or maybe some other "cheaty" tricks to grab a desired domain name?

As for that part, do you sincerely believe that if someone found out the miracle solution to win things like that 100% of time, they will share it there (or any other website) with any stranger? I doubt so.

Final advise, even if you did not ask for it: your life will probably be simpler and "lighter" if you do not concentrate so much on any given name, and just shop around in other TLDs and other names (if the one you want becomes taken too fast), as many endeavours/business can work the exact same way whatever name they are using.