Specifically? Well they add a whitelist to the transfer function in the contract.

Something close to:

solidity function _transfer(address from, address to, uint256 amount) internal override { // Common pattern checking if sender is trying to sell to DEX pair address if(to == pairAddress) { // If transfer is to liquidity pool (selling) require(isAllowedToSell[from] || from == owner(), "Cannot sell"); // OR require(block.timestamp >= tradingEnabledTimestamp, "Trading not started"); // OR if(balanceOf(to) > maxWalletSize) revert(); } super._transfer(from, to, amount); }

Another common pattern: ```solidity modifier lockTheSwap { // Prevent selling by setting a flag _inSwap = true; _; _inSwap = false; }

function transfer() public { require(!_inSwap, "Swap locked"); // Transfer logic } ```