Confused how to do some modification? This guide for all, from beginners who need expertise to get started, to advanced players who need to rearrange their plugin folders. If you are layman to SimCity 4, check out the official manual at the Maxis Files for SimCity 4 page on Simtropolis.
As a complex city simulator, features in SimCity 4 can be expanded using plugins. But, there are important things to do when adding and removing plugins: keep it simple, check dependencies and read the readme first. As a starter, you should start simple and gradually advanced. Don't rush yourself to install advanced mods. When installing mods, always check their dependencies using the BSC Cleanitol or the site-provided dependency tracker. Failed to do so can result of brown boxes to even a crash-to-desktop (CTD).
Here are mods you should install in the first day:
Network Addon Mod
One of the most downloaded and important mod. NAM adds new features and fixes bugs regarding networks, from granular traffic simulator, diagonal streets, pedestrian malls, stations to realistic highways.
Being a DLL mod, SC4Fix is bringing important fixes: hovering transit-enabled lots (allows appropriate networks to connect) with NAM puzzle pieces fix, allows non-GZCOM DLL to be loaded to the so-called prop pox (props not shown in circumstances) fix.
Extra Cheats https://community.simtropolis.com/files/file/21118-SimCity-4-extra-cheats-plugin/
Internally used by Maxis and released by @Buggi, Extra Cheats is bringing tons of cheats: precisely set money, unlocking locked buildings, plop buildings with ease and so much more!
Crime Doesn't Pay
Reduces crimes into a controllable level. It also can be used to deal with overproduced crimes by badly-made buildings.
I-HT Missing Jobs Fix
Fixes bug regarding to missing $$$ jobs generated by I-HT buildings due to a rounding error. To install this mod correctly, follow the instruction at https://community.simtropolis.com/forums/topic/48632-tutorial-applying-the-i-ht-bug-fix-correctly/ carefully.
Maxis Prop Names Fix
Includes prop-version of vanilla buildings (bldgprop_vol1.dat) and Rush Hour/Deluxe (bldgprop_vol2.dat). Also, it also includes an assortment of building props Maxis had forgotten (Plugin_landmarks_and_other_missing_Props.dat).
Opera House Fix
Fixes inhibited city growth due to Opera House overcapacity by increasing the capacity to larger number.
Private Schools with Sliders
Again, fixes inhibited city growth due to Private School overcapacity by adding the funding and school bus sliders.
To be noted, DLL files can't be installed in subfolders. For instance, if you place at Documents\SimCity 4\Plugins\Essentials (assuming the default location), they'll not work. You should place it right into the Plugins folder.
If you want more fixes to your game, here are the mods you needed:
Real Upgradeable City Halls
Minimize Button Remover
SMP Yellow Pause Thingy Remover
Allows you to be funded by (imaginary) companies or non-government organizations.
Friendly Business Deal
City Hall MMP Fix
Fixes the annoying problem when non-flora Mayor Mode ploppables (MMPs) accidentally will be chose by the buildings automatically and reducing the building's aesthetics.
Allows you to see the city population precisely. Although this mod requires 2 dependencies, this mod is worth to use.
If you want to customize the water, terrain, rocks or even the slope control, it's fine to do in the first day as long as you don't spend time too much on it. In fact, there are shoppes (except for the slope, but you can Google for it) by @CorinaMarie to customize them.
If you want to install Colossus Addon Mod (CAM), Daeley Advanced Menu Navigator (DAMN. Yes, it is) or similar mods, you should only install them when you mastered enough the game, typically 3 real-life days or more.
If you have constructive suggestions, critics or found mistakes, please send them in the comment section or send me a PM.