Working on some execution optimisation related backtesting. I have so far been executing with market orders only. Going towards higher lot sizes, I'd like to optimise for minimal slippage.

First off, on NSE, if you place a market order, you get filled at the best bid/ask right?

If we want to optimise this, the first non-creative idea one can think of is, slicing the order into different lot sizes, and placing a limit order for each slice at the mid point of current best bid & ask.

But this requires your latency to be the least.

Why would latency affect it?

I looked at tick historical data, and there are more than 18-20 ticks in a second (auction and quote combined).

Even if you keep 10 ticks per second, your best bid/ask can shift from the time you place to the time exchange receives the order.

So, the next best thing that people can do is place tranches of orders every 1s, 3s, 5s, 10s, 15s - in their preferred time range, and get filled at the midpoint or best-bid+1/2/3/4/5 in the depth.

What you need is liquidity.

But if you're trading breakouts, then it's highly likely that your limit orders may not get filled if the action is too fast.

So, a retry mechanism is required in such cases.

If nothing works, you convert your orders to marketable and get filled at worse slippage.

50 rookie mistakes to avoid as a stock market beginner - a thread.

1. Watching CNBC and acting on the recommendations provided by the "analysts", "experts" and "fund managers" who appear on TV.

Remember, most of them don't even beat the benchmark index on an annual basis.

2. Giving too much importance to Moneycontrol articles and recommendations. Moneycontrol profits off of noobs. They depend on you to make their money. They get paid by buy side firms who want to dump their positions, and sell side firms whose clients want to sell.

They also get paid to propagate rumours (albeit subtly) about stocks that the buy-side firms want to buy (albeit at lower prices) and sell-side firm clients want to buy. So, if you see a recommendation on moneycontrol, that marks the distribution phase (most of the times).

3. Listening to colleagues, friends, and family on what to invest on, where to invest, what stocks to buy. Usually these are also people who have no real expertise, but started a year or few months ahead of you. They only talk about their winners, you get very excited.

4. Listening to social media "experts". People on Twitter, Youtube, etc., even if they look like they are trading crores, or managing hundreds of crores, have different reasons for trading/investing in something. Typically, following them is the path to the butcher's shop.