Do not chase fund managers. They all have good periods and eventually will have a bad period.
Think about high charges - how many companies are taking a slice of your 'investment pie' - e.g. fund manager, fund platform, financial adviser.
Think about consistency of a fund in its sector. Always look for consistent above average and ideally top quartile performance over multiple periods.
Don't disinvest from a usually consistent fund in its sector just because it had a 'poor' three months.
Be aware that bigger 'supertanker' funds cannot react quickly to adjust portfolio mix and holdings compared to smaller funds. If you have £10bn (£10,000,000,000) in an investment fund and decide to move just 5% from one sector to another - it's not easy to sell £0.5bn (£500,000,000) of stock in 1 or 2 assets and reinvest the same in other assets without creating market ripples of
Don’t 'have all your 'eggs in one basket'.