Voice activated recorders are small enough to be hidden just about anywhere. The key is to find a suitable location so that there is minimum disturbance and maximum clarity. You can hide it on your person or in the room or in the area that the conversation is going to occur. Most recorders are digital voice activated recorders which are very convenient and has considerable storage.
On your person the best place to hide is inside the shirt or if it is a small digital voice activated recorder you can leave it in your pocket. Some are usually small so that you can clip it to your sleeve. If you are going to have a conversation in a room you can hide it in the book case or on a shelf near the area of conversation. Spy Digital Voice Recorders can be clipped under the table or chair where the conversation is going to happen.
The key here is to understand and judge the situation. If you can first size up the situation and the environment you will be able to find some suitable places. The voice activated recorder fits perfectly into most nooks and corners in the room or the furniture. If you are outside you can hide it under the chair or table. If you are definitely going to be present then it is best to hide it on yourself so that you can ensure the recorder does a perfect job. You can move around and since most of the voice activated recorders are portable nowadays it becomes very convenient.
If you are not going to be present you have to have a clear idea of the situation and assess the environment careful. Would the target be sitting or standing or doing both intermittently? Would the wind be high and causes a disturbance say for example on the sea side or will there be traffic noises that would cause problems? A good way is to be in that environment and observe .Once you find out the area where the conversations are most likely to be, hide the recorder in the closest and the most unlikely place possible.