The road to production for a parachain can be a daunting process. Luckily, there is a clear path to progression from prototype, to testnet, to canary (if desired), to production.
The following is mostly based off of common approaches that have been implemented over the years by different parachains within the ecosystem.
Parachain Development Funnel
A parachain usually goes through the following "development funnel" from prototype to production:
Most parachains within the ecosystem have adopted this pattern of deployment. This guide shows you how to accomplish the first part with a setup catered to local development. After this, it is typical to look to deploy to a testnet, such as Rococo. After that, most parachains opt to either go directly to Polkadot, or setup a canary network on Kusama.
There are quite a few parachains which have networks both on Kusama and Polkadot.
Most parachains use Kusama as a 'chaotic' testing ground for ensuring their network work in a production-like setting.
There are a number of different parachains to reference. All use Substrate as the base, but have varying implementations depending on their usecase. You may find a comphrensive list of these parachains on parachains.info.
Parachain Design Decisions
When building a parachain, there are a number of design decisions that go beyond pure code. Parachains should be concerned with maximizing the blockspace they purchase.
In order to do this, more elaborate schemes containing game theory and economics are often involved to ensure the parachain itself remains self-sufficient within its own means and domain-specific functionality.
The parachain's consensus and finality is guaranteed by Polkadot, yes. However, the parachain itself is responsible for the business logic, whether it chooses to incentivize its collators, any staking mechanisms, and any other domain-specific logic. It is possible for an attacker to exploit a parachain's mechanism if it isn't designed well or contains a vector for attack.
Game Theory & Economics
To learn more about applied game theory and economics aspects, check out the Polkadot Blockchain Academy's section on it.
Collators are necessary to keep the parachain syncing and finalizing with the relay chain. A parachain only really needs one honest collator at minimum, however, it is advisable to have more to ensure resilience.
Stuck with an issue? Ask on StackExchange
If you get stuck on a technical issue, make sure to ask on The Substrate Stack Exchange. It often has those more acquainted with the protocol ready to answer any technical questions.
If you want to get feedback for an idea or consult the wider ecosystem, feel free to post on the Polkadot Forum.