A condensed set of rules (drawn from the C++ Core Guidelines) that keep modern C++ safe, readable and fast.

Resource management

Types & interfaces

Make things const by default — variables, parameters (const T&), member functions.
Prefer enum class, std::array/std::vector, std::string_view/std::span for views, std::optional for “maybe”.
Mark single-argument constructors explicit; mark overrides override; give polymorphic bases a virtual destructor.
Pass cheap types by value, others by const&; return by value (move/elision make it cheap).
Use strong types instead of bool/int soup: setTimeout(Seconds{5}), not setTimeout(5).

Expressions & control

Initialise every variable at declaration; prefer {} to catch narrowing.
Use auto to avoid repeating types, not to hide important ones.
Prefer algorithms and range-for over index loops; prefer std::ranges:: versions in C++20.
Use named casts (static_cast) and minimise them; never C-style casts.
Keep functions short and single-purpose; limit scope of variables (if (auto x = …; cond)).

Tooling

Tool	Why
`-Wall -Wextra -Wpedantic -Werror`	Catch mistakes at compile time
ASan / UBSan / TSan	Catch memory errors, UB and races in tests
`clang-tidy`	Static analysis, modernisation checks (`modernize-`, `cppcoreguidelines-`)
`clang-format`	Consistent formatting, no style debates
CMake + a package manager (vcpkg/Conan)	Reproducible builds and dependencies
GoogleTest / Catch2	Unit tests

Idioms worth knowing

C++

#include <iostream>

template <typename Derived>
struct Shape {                                           // CRTP base
    double area() const { return static_cast<const Derived&>(*this).areaImpl(); }
    void describe() const { std::cout << "area " << area() << '\n'; }
};
struct Square : Shape<Square> {
    double s;
    explicit Square(double x) : s(x) {}
    double areaImpl() const { return s * s; }
};

int main() { Square{3}.describe(); }                     // resolved at compile time, no vtable

Output

area 9

What is CRTP and why use it?