In general, any public places in Lithuania may be pictured and taped for private use, while in private areas the owner decides what could be pictured.
Under the Soviet occupation, photography was heavily restricted even to the few that owned cameras. Most of these limitations were abolished, but it remains forbidden to take pictures at the international airports. When taking pictures of other key infrastructure (especially the railways) one may still get some interest from the security, although it is no longer that restricted.
Private shopping malls, marketplaces, casinos and nightclubs usually ban taking images - while this policy may be not explicitly stated anywhere, the security enforces it. While it may be possible to take a quick selfie or picture your friends without generating attention, any longer "photo shoot" will surely attract it. Chain stores tend to especially hate when their price tags are pictured, even if on the background.
Most museums allow photography but some forbid, while an even smaller minority levy a fee on every camera. Usually this is specified near the entrance (otherwise, you may ask).
In the case of live events (concerts and professional sports), the rule of the thumb is that only the most expensive, important and popular ones ban taking images. E.g. it will likely be forbidden to take pictures during official international basketball games but allowed during friendly matches or national league games.
Lithuanians usually don't care that they are photographed in public and they don't expect anything in return for it. Photography of private areas (even if visible from public zones), such as yards, may cause concern - but it is not very likely. The overall rule of the thumb is simply not to be too intrusive and take pictures from a distance or, if a close-up is needed, then ask the person.
It is not advisable to take pictures of drunk people (especially in the evenings) as they may be looking for a fight.
In case you want to publish pictures more stringent rules may sometimes apply. Some museums that allow free private photography impose a fee on those who want to publish images. Additionally, it is forbidden to publish pictures of people without their permission (even if taken in public) if those pictures show them in compromising situations or are used for advertisement.
Specialized photo stores became rare after digital imagery displaced the analog one. However, memory cards, batteries, and other photo materials may be easily acquired at electronics stores, common at shopping malls.