Know what must happen
A both-teams-to-score selection normally requires each team to score at least once in the period covered by the market. Check the operator’s rules for the relevant period, abandoned matches and own goals. A high total-goals expectation alone does not establish that both teams will score.
Read attack and defence together
Examine how each team creates and concedes chances. Pair a side’s scoring record with its opponent’s defensive record, but do not simply average two historical percentages and call the result a forecast. Those samples may include very different opposition.
Treat streaks carefully
Six consecutive BTTS results describe six matches; they do not make a seventh inevitable. Home and away splits, personnel and match incentives can all matter. Note the size of the sample next to every percentage so a short run is not mistaken for a stable pattern.
Compare the market terms
BTTS for a full match and BTTS in the first half are different products. Bet-builder combinations can also introduce dependence between selections. Compare equivalent markets and read how each operator settles them.