Let mamma cat have a dark, quiet place to nest. You can provide a nest of old blankets; she may drag them somewhere that she finds more suitable.

The two females I've had give birth in my home were both unassisted, no breeches or any other troubles. Bosun did have one stillborn and three healthy kittens. Make sure mamma bites off the cord; if she doesn't you can cut it and use a styptic (sp?) pencil to stop bleeding.

For the most part, just observe and let her do her job. Do you know if she's had other litters?

If mamma allows it, start touching the kittens as soon as possible. This helps socialize them; they get used to your scent. Scent is their primary scent cue for the first 10 days of life or so.

Good luck! Raising kittens (or watching mama raise them) is so rewarding!