On arrival, ensure that you are happy with the room's location and standard: now is the time to negotiate improvements. A smile and civil behaviour should ensure that you receive the service you desire. Issues should be taken up with reception; only resort to speaking to the manager if you reach stalemate.
Always be polite to hotel staff. If you call for room service, ensure that you're presentable, and be ready with a small tip in smarter hotels.
If running late when checking out, a call to reception should secure an extra hour or two. Don't help yourself to bathrobes, fixtures and fittings.
On an extended hotel stay, ensure that the maid doesn't change linen every day - instructions are usually given in the bathroom. Leaving used towels on the floor or in the bath is an invitation to have fresh ones substituted.
In the past, tips would be expected by doormen and porters on every interaction. Increasingly, this is a judgement call, dependent on the quality and speed of service, and the level of expectation of the hotel and its staff. Seasoned travellers often choose to give something at the beginning and end of their stay; they will also be well-prepared with small notes and change for quick tips.
Check whether a service charge is included in your room service bill. If you are not leaving a single large tip at the end of the stay, then it is usual to tip when the order arrives.