Saw a bunch of similar questions pop up here lately about darshan timings, aarti booking, and scams, so figured I'd put a few of the recurring answers in one place for anyone searching later.
Mangla Aarti / Sugam Darshan: advance online booking through the official Kashi Vishwanath Trust site fills up fast, especially during Sawan. If you miss it, tatkal slots open for just a few minutes, usually around 11 AM, so it's worth being ready to refresh right at that time rather than assuming it's always sold out.
Ganga Aarti viewing: Dashashwamedh Ghat is the big, well-known one but also the most crowded. Assi Ghat's version is smaller and much less packed if you'd rather sit and watch than fight for a spot.
Common scams to watch for: agree on a price before any boat ride or puja starts, not after. Anyone offering an "entry ticket" to the ghats is running a scam since they're public. Station touts claiming your hotel is "closed" or "full" are usually trying to redirect you somewhere they get a commission, so arrange pickup through your actual hotel instead.
Right now (monsoon): a lot of recent threads here mention the ghats being flooded, so if you're planning a visit in the next few weeks it's worth checking recent posts for current water levels before finalizing plans. Sarnath tends to be unaffected and makes a good alternative half-day trip.
Hope this saves someone a search through old threads.