While Costa Rica is, in general, a very safe country, pickpocketing and petty theft can be a problem. Applying basic common sense will mean you avoid the hassle of lost belongings.
Firstly, never leave items on show in your parked car. If you're heading to the beach try and park in a carpark (some are guarded by enterprising locals) or near other cars.
Next, be aware that pickpocketers operate at bus stations and other crowded places like markets. Don't leave your bags unattended, and if you are unlucky, report the theft at the local police station.
Petty theft (including bag snatching) is one of the most common types of crime in Central America. There are some common scams around, especially the taxi cab scam where a driver tells you the meter is broken once the drive has already begun.
The people who do tend to be involved in some sort of incident are usually drinking or doing drugs or taking part sex tourism. It's your best bet to avoid those activities if you want to say safe.
Always trust your gut instinct. Avoid isolated areas at night, and be aware of your surroundings at all times. Make copies of your personal documents, including your passport and ID. Forward your itinerary along to loved ones so they’ll know where you are.
The most important piece of advice would be to purchase good travel insurance. Travel insurance will protect you against illness, injury, theft, and cancellations. It’s comprehensive protection in case anything goes wrong.
Costa Rica is one of the safest countries for traveling and backpacking in Central America, it’s always good to play it safe!