Noordwijk aan Zee can be found about an hour from Amsterdam and The Hague.
From Schiphol you can follow the A4 motorway to the direction of The Hague. At the junction after the bridge restaurant and the petrol station, head towards Leiden West/ Den Haag Centrum on the A44
On the A44 take the exit Noordwijk/ Voorhout/ Oegstgeest Noord.
To get from Amsterdam, first take a train to Leiden Centraal (35min.; 8 per hr.; €7.60). Outside the station in Leiden is a terminal where you can catch bus #40 or 42 to Noordwijk (30min., 5 strips or €2.20).
If you don't own a car or a bicycle propably the best (and only) way to get to Noordwijk is by bus. (Ok, you can take a taxi, but...)
You may first take the train to Leiden (Centraal), which is approximately 12...15 km from Noordwijk. From there you can get to Noodwijk by buss number 40 or 42, which takes about 20...30 minutes. 40 and 42 have different routes, but they both will take you to Noordwijk aan Zee's centre.
Also busses number 90 and 95 (from Haarlem to Haag and vice versa) go through Noordwijk.
There are quite a good train connections to Leiden. Both buses 40 and 42 go twice in an hour on weekdays and on saturday and once in an hour on weekends. Bus may seem to be a bit expensive when paying with cash (4 euro from Leiden to Noordwijk), but you could also use 'strippenkaart', which will get you there little cheaper. (Check out 'Transportation' at my Netherlands page for information about 'strippenkaart'.)