Warframe has an official website for news as well as community forums where players can login with their Warframe Account:
https://www.warframe.com/
https://www.warframe.com/en/community <--- Notice the en means English in this URL, change for different languages.
The Warframe Wiki used to originally be hosted on Fandom but has since been moved to the new Wiki. The wiki contains information on quests, missions, hidden things, and drop sources:
https://wiki.warframe.com/
Especially helpful imo are the Dialogue Trees listed in the Kinematic Instant Messenger categories (The PNG Charts at the top of the page are more legible / in depth / complete):
https://wiki.warframe.com/w/Kinemantik_Instant_Messenger
Another useful tool is Overframe, a collection of equipment builds maintained by the community to maximize your effectiveness. Just search the weapon or warframe you want a build for:
https://overframe.gg/
Lastly is the Warframe Player Market (not to be confused with the ingame market terminal). Technically, there is no official market, they're all third party, but the one market which reigns supreme is this one:
https://warframe.market/
It contains a tool for buying prime bps worth the most ducats/plat.
On that note, new players should know that almost all ingame trading is done via Platinum, an ingame currency which CAN be obtained by Free To Play players via trading, or can be purchased officially from Digital Extremes via real world money. It's the sole monetization policy of Warframe, it keeps the servers up and content coming.
Items worth the most plat:
/1. Unveiled Riven Mods:
Some riven mods can auction on the market via the contracts menu for hundreds of plat. The most valuable are a 3 stat mods with 2 positive and 1 negative (an inconsequential negative) for a decent weapon. Most rivens are not that valuable, unfortunately.
/2. Prime Parts / Blueprints:
Opening Relics can net you some profit if you're lucky, but it's not consistent. Good source of relics are: running the Elite Onslaught with Cephalon Simaris, the 2nd zone completion has a chance of a Radiant Relic and then you just let the portal expire instead of moving to the 3rd zone. Another good source is trading Aya for the unvaulted relics on rotation via Maroo's Bazaar. Note that Relics are NOT random mission rewards, some relics MUST be obtained from specific missions on specific reward rotations.
/3. Rare Mods:
Corrupted Mods, Lua challenge vault mods, and Cannonades are all worth at least a little platinum and it's always good to grab a copy or two of each mod for personal use.
FAQ:
Q: How do I get more credits?
A: The Index
Q: How do I deal more damage?
A: First better weapons, then damage multipliers, and then debuffs. Also arcanes but we don't cover that here. Kuva, Coda, and Incarnon weaponry are the meta currently so just keep progressing the quests as much as you can. As for damage multipliers, it's almost always better to follow a community build but generally you're just trying to find the optimal mix of: direct damage modifiers (either elemental or physical) > faction damage multipliers > critical damage modifiers > weakpoint damage modifiers > Multishot. After that comes debuffs. Elemental status effects can do things, most enemies have a specific weakness, but particularly useful against higher level enemies than yourself is: Slash - Causes bleed and True Damage, Radiation - Causes enemies to fight each other, Corrosive - Reduces enemy armor, Viral - Multiplies damage to health (not shields) by up to 325%, and Magnetic - Effectively damages shields and only shields. FUN FACT: Critical Chance can go over 100% which will guarantee a critical on every hit and sometimes give a double critical "red crit", and you can even go to a level even further beyond when you reach over 200%.
Q: How do I gain mastery?
A: Firstly you can rank weapons, warframes, companions, kitguns, zaws, archwings, necramechs, etc to rank 30. A select few weapon types can overlevel by adding formas up to rank 40. The best place to level items is Cephalon Simaris Elite Sanctuary Onslaught Zones 1 and 2 on repeat. You can check your progress on your profile under equipment tab. A lot of equipment can be obtained for credits on the ingame market terminal in the orbiter bridge, or from the labs in a player clan dojo. Secondly, you get mastery from completing the Star Chart and again in Steel Path. Thirdly, you gain mastery from completing Factions such as The Hex, Cetus, Vox Solaris, the Quills, etc.
Q: How do I get more endo?
A: Try to get Legendary Cores whenever they are available via the void trader or limited time events called Epoch Operations. Some mods can cost either 40K Endo or 1 Legendary Core, your choice. Other than that, the lowest level way to get endo is on Sedna - Vodyanoi (Arena) and the better option is to find players running it in Steel Path with specific warframe loadouts to maximize loot and key positions to force enemies to spawn in one specific area (and then instantly die). Some video tutorials are available online.