Birmingham - England captain Andrew Strauss has said his side are becoming increasingly comfortable with cricket's controversial Umpire Decision Review System (DRS).
The system is being used in a Test series in Britain for the first time during the ongoing four-match campaign between England and Pakistan.
England had much the better of the review system during the first Test at Trent Bridge where they won by the huge margin of 354 runs and will hope for a similar outcome in the second Test, starting at Edgbaston here on Friday.
Each side is allowed two unsuccessful challenges per innings under DRS although they only have a supposed maximum of 15 seconds in which to request a referral of an on-field decision to the third umpire who, assisted by various technological aids, then rules on whether to overturn an on-field verdict.
"It's still a challenge to know which ones to review and which not to," Strauss told reporters at Edgbaston here on Thursday.
"We reviewed one for Graeme Swann that was going down leg and didn't ask for one off Jimmy Anderson that was hitting leg.
"Everyone is getting more used to the system now," the opening batsman added.
"The umpires don't seem to be taking offence if a decision is overturned and generally we're getting more decisions right on the back of it and that is a good thing.
"I am getting more used to which player's judgment I can trust too," Strauss said, without revealing the identity of his DRS advisors.
There is always a risk that DRS referrals can be squandered by batsmen desperate to keep their innings going at all costs, only for replays to prove the on-field umpire was entirely correct in his original decision.
Strauss said the non-striker had a key role in helping a team avoid speculative referrals that had little chance of success.
"There's always a part of you as a batsman that thinks it isn't out, but the guy at the other end has to be honest," he explained.
"You are not going to get every one right and there's still a reason for the top-order to use a review if it's fifty-fifty, more than the tail. But we're getting to grips with it and understand the mechanisms better."