When a glass ampule is opened the needle (on a syringe) can be entered directly and gentle outward traction on the plunger of the syringe will draw up the contained liquid.
When a container with a rubber stopper is encountered, the needle can be entered through the clean rubber stopper and gentle traction on the plunger of the syringe can usually draw up the liquid that is contained. When the needle is too short to reach the bottom of the bottle, it is often helpful to turn the bottle upside down to bring the liquid to the tip of the needle.
Note that since the rubber stopper container system is “closed” to the outside air, the pressure within the bottle will be reduced when its contents are withdrawn (aspirated into the syringe). If a larger volume is to be withdrawn the pressure gradient created can make aspiration difficult. In these situations, it is generally easiest to initially draw air into the syringe (an amount of air roughly equal to the amount of liquid to be withdrawn) and inject this air into the container prior to removing the desired liquid.