When to go:
If you want to enjoy snowfall and chilling whether then December to March is the best time to visit and if you're not much of winter person then one can visit from April to September where temperature is moderate(also one can see apple farming)
Where to stay and eat:
There are lots of options available and one must try local cuisines. However I would highly recommend to stay in a homestay as it is relatively cheap and excellent food is served( not to forgot their local cuisines are highly delicious)
In short if you're planning to visit Manali then this should be definitely on your list.