An eighth is a strong starter dose (assuming moderately potent shrooms). Do not panic in any way, just keep calm, and stay in a stable and controlled environment. Have a sitter with you that knows what the hell is going on and can be trusted no matter what. Big streets are a nono (lol, personal experience).

Don't eat for 12 hours or so before eating the mushrooms and eat the mushrooms all at once (one sitting, not one mouthful). They should kick in swiftly and powerfully then.