• BakerBridge
• CONVENTIONS
• Takeout Double
• Blackwood
• Weak 2-Bid
• Strong 2-Club
• Stayman
• Negative Double
• Reverse Bid
• Gerber
• Jacoby Transfer
• Weak Jump Overcall
• Michaels Cue Bid
• Unusual Notrump
• Support Cue-bid
• Weak Jump Shift
• Help Suit Game Try
• Jacoby 2NT
• Splinter Bid
• RKC Blackwood
• Fourth Suit Forcing
• New Minor Forcing
• D.O.N.T.
• Reverse Drury
• Lebensohl
• 2 / 1 Game Force

When partner opens 1 of a Major suit there are standard ways for you to support that suit.
But if an opponent intervenes with an Overcall the situation changes. A very good method to follow is to treat all direct raises as weak, (less than 11 points), but to let the raise indicate how many trumps you have. With 3 trumps you bid 2 of the suit, with 4 trumps jump to 3, and with 5 trumps jump to game. This has a preemptive effect but also might get you to a good contract.

If you do use this method in competitive situations, then you need to have a way to tell Opener when you have a good hand with support for his suit.

An immediate cue-bid of the Overcalled suit shows good trump support and at least 11 points - this is referred to as 'Limit Raise or better.'

Lesson available.
Also see lesson on Law of Total Tricks for more about the weak raises in first paragraph.