What should beginners compare before choosing an F&O broker?

What should beginners compare before choosing an F&O broker? Starting out in F&O trading, the biggest confusion I had was around brokerage costs and margin policies. Flat‑fee brokers like HDFC Sky make it easier to understand what you will pay, ₹20 per order or 0.1%, and their margin trading facility is a straight 1% monthly (\~12% p.a.) with a holding period of up to 999 days. Compare that with full‑service rivals like ICICI Direct or Kotak Securities, where brokerage is percentage‑based and MTF interest often creeps above 15–18% p.a. Add in shorter holding periods (usually capped at 365 days) and restrictive eligible stock lists, and beginners end up paying more without realizing it. Platform reliability is another factor, legacy bank‑backed systems are clunky and slow, while discount brokers at least give you modern apps, even if they sometimes suffer outages during high‑volume sessions. Hidden charges like DP fees, AMC, and call‑and‑trade costs also pile up, especially with traditional brokers. For anyone just starting out, the comparison isn’t about fancy research reports or brand names, it's about whether you are paying flat vs percentage brokerage, how transparent the margin interest is, and whether the platform lets you hold positions long enough without forcing an early exit.