Standard format to store text in LSB steganography? I am trying to understand how text is stored in images in LSB. 

If we consider a 24 bit image, we have 3 values per pixel (RGB). So we can store 3 bits in a pixel. So how do we store 'A' or any other character in this situation? Do we store 6 bits in 2 consecutive pixels and then last 2 bits in RG of next pixel and then start storing the first bit of next character from B of the same pixel? 

Also, is there a standard for this? E.g. should we start from the first pixel always? If not, is there a way to guess by looking at the pixel values from where the data is stored?
There is no standard. But since the goal of steganography is undetectability, it is not usual to hide data into consecutive pixels. Steganography hiding data into all the pixels is broken.

Some algorithms use a function that detects areas of the image where the insertion produces less distortion along with a PRNG.

See, for example:
https://hal.archives-ouvertes.fr/hal-00541353/document