About 99.99% of trams will have a ticket inspector. Board the tram at the rear and have 3 euro ready to pay (it is best to have a Dutch chip card since then you pay for a distance and not per ride - and for few stops you will pay between 0.5 - 1 euro instead of 3 without it). The inspector (wearing an ugly yellow and black jacket with green, red and purple stripes) will have to walk the length of the entire tram checking tickets before he/she reaches you. Hopefully you have reached the stop by this time, if not just give the inspector the 3 euro for the ticket as though you were waiting to buy one from them. This is common practice.
The Metro is harder to blackride, you'll have to follow somebody going through the gates very closely. Make sure nobody's watching, though. Or, if there is elevator, which probably will be somewhere close to station, but not near the main entrance. Next to elevator it will be OV-Chipkaart terminal and no gates. In lot of stations there are no security, as lot of them looks like traditional railway stations.
- Train: Thalys
There is a big forest in Kralingen called Kralingse Bos (next to the lake Kralingse Plas). Very beautiful area, close to the city center (nearest metro is Voorschoterlaan), just find your spot.
If you take tram 23 from Rotterdam Central to the stop P+R Beverwaard in the Ijsselmonde suburb, there is some small forest along a bike trail parallel to the A16/E19 motorway where you could put up a tent.
If you take tram 25 all the way to terminus "Barendrecht Opstelstoor Carnisselande", you can cross the river and there's plenty of quiet bushes and small forests. Also, you are nearby a great spot to get on the A29.
Most McD restaurants in the city have wi-fi and, if you are discreet, you can use them without buying anything. The central library also has free wi-fi. Get a "guest pass" from the machine on the ground floor and log in with the details printed on it (the library connection, however, blocks everything but port 80 -- that is, except simple web browsing). Also, central station have many shops with free wifi access.